Pyrotechnic cutter apparatus

A pyrotechnic cutter for cutting an object such as a buoy-rope, tube, cable or the like and adapted to be mounted on a submarine vehicle, and including a fixed arm containing an explosive charge having a dihedral covering, and a second arm pivotally mounted to the fixed arm through a body portion which operatively engages an ejector which is adapted for engagement in the free end of a gun barrel, the ejector having an electrical circuit and a pyrotechnic circuit for ejecting the body having the arms, and detonating the explosive charge after a suitable time lag, so that explosion of the charge cuts the object.

The present invention relates to a pyrotechnical cutter the charge of which 
has a dihedral covering or casing and, in particular, to a cutter designed 
to cut the buoy-ropes of marine mines. 
It is already known to employ pyrotechnical cutter, towed by ropes behind 
mine-sweepers, for cutting the buoy-ropes of marine mines which then 
ascend to the surface where they are destroyed. By way of example, cutters 
of this type are disclosed in French Pat. Nos. 1,604,952, and 2,114,409, 
and in British Pat. No. 1,336,080. 
In the remainder of the description, consideration will more particularly 
be given to a cutter which is not intended to be towed rearwardly of a 
mine sweeper, but which is designed to be disposed individually on a 
pre-determined buoy-rope, tube or cable, prior to cutting that buoy-rope, 
tube, cable or the like. 
Consequently, it is one of the objects of the invention to provide a cutter 
wherein the cutting is achieved by a hollow charge effect, thereby 
substantially increasing the depth at which the cutter may be utilized. 
It is a further object of the invention to provide a cutter which may be 
mounted on a submarine vehicle or submarine device guided by a wire and 
capable of transporting the cutter up to the buoy-rope to be cut, of 
depositing the cutter on the rope and, finally, triggering functioning of 
the cutter after a pre-determined period of time enabling the submarine 
device to be recovered or efficiently removed. 
A further object of the invention is providing a cutter affording, during 
manipulation thereof and during transport thereof by the submarine device, 
the achievement of maximum security againt untimely functioning. 
A further object of the invention is providing a cutter in which the hollow 
charge is a charge having a dihedral covering or casing. Dihedral charges 
or the like generally, are already known, for example as described in 
French Pat. Nos. 2,071,315 and 2,082,934. The dihedral charge produces a 
practically identical cutting effect over its entire length. 
According to one feature, there is provided a pyrotechnical cutter one of 
the arms of which contains a dihedral charge over practically its entire 
useful length, the plane of symmetry of the dihedral, i.e. the plane of 
the cutting jet of the charge, being directed toward the other arm of the 
cutter, and the explosion of the charge cutting any object enclosed 
between the two arms. 
According to a further feature, there is provided a dihedral charge cutter 
initiated at one end and simultaneously at three points which are not 
aligned, one of which is in the plane of symmetry of the dihedral, near 
the edge thereof, whereas the two others are disposed symmetrically 
relative to said plane of symmetry. 
According to a further feature, the cutter which is designed to be mounted 
on a submarine device comprises an ejector adapted to be engaged in a gun 
barrel fastened to the submarine device, a body fastened to the arm 
containing the dihedral charge and on which the second arm is articulated, 
the body being separated from the assembly of the barrel and of the 
ejector at the instant of functioning of the ejector, the body carrying 
means for controlling the opening and closing of the arms of the cutter, 
said control means maintaining the arms open for as long as the ejector 
has not functioned and closing the arms as soon as the body is separated 
from the barrel-ejector assembly, said separation triggering in the body, 
after a pre-determined delay, initiation of the dihedral charge of the 
first arm. 
According to a further feature, the ejector-body assembly is able to rotate 
in the barrel and to adopt two positions, one wherein said control means 
takes a third inoperative position while closing the arms, and the other 
wherein said control means functions as indicated hereinabove. 
According to a further feature, the means for initiating the dihedral 
charge comprise an electrical circuit and a pyrotechnical circuit, the 
electrical circuit comprising a source of primary energy, a delay circuit 
and a switching circuit, the source functioning subsequent to ejection of 
the body and transmitting a signal to the delay circuit the output of 
which feeds the switching circuit, the pyrotechnical circuit comprising a 
detonator and a pyrotechnical relay capable of exciting, along three 
paths, the explosive disposed at three initial points of the dihedral 
charge, the switching circuit feeding the detonator. 
According to a further feature, the source of primary energy comprises 
primary cells adapted to be primed by sea water and disposed in a 
fluid-tight cavity for as long as the cutter is not deposited on the 
buoy-rope. 
According to a further feature, the switching circuit is controlled 
mechanically by a hydrostatic piston which, in the inoperative position, 
short circuits in the switching circuit the wires connected to the input 
of the detonator and opens the wires connected to the output of the delay 
circuit and which, in the operative position, reached when the hydrostatic 
pressure applied is sufficient, connects the wires of the output of the 
delay circuit to the input wires of the detonator. 
According to a further feature, the piston comprises a head which, in the 
inoperative position, projects externally of the body, the said head 
comprising a groove in which is lodged either a locking clip or a heel 
fastened to the second arm when it is open, in such a manner as to 
maintain the piston in the inoperative position and to prevent the piston 
from accidentally being depressed. 
According to a further feature, the central portion of the piston is 
disposed between the detonator and the pyrotechnical relay, having a solid 
portion providing a screen between them when the piston is in the 
inoperative position, and an orifice permitting action of the detonator on 
the pyrotechnical relay when it is in the working position. 
According to a further feature, the gun barrel comprises two pins aligned 
parallel to the axis of the barrel-ejector-body assembly, and the means 
for controlling the opening and closure of the arms comprises a sleeve 
adapted to slide without rotating on said body, the sleeve comprising a 
collar in which, at the same distance from the axis as the pins, there are 
formed on the one hand two dimetrically opposite cups which are, however, 
offset through 90.degree. relative to the notches, said sleeve being 
constantly urged toward the ejector by a spring and the ejector-body 
assembly being, in the initial inoperative position, oriented in such 
manner that the pins of the barrel pass through the notches in the collar, 
thereby permitting the spring to urge the sleeve close to the ejector to 
close the arms and, in the working position, after having rotated through 
90.degree., oriented in such manner that the pins have their ends bearing 
in the notches of the collar, thereby maintaining the sleeve away from the 
barrel. While compressing the spring and resulting in opening of the arms 
and, once the body has been separated from the ejector, the sleeve is once 
again urged by the spring, to again close the arms. 
According to a further feature, the second mobile arm is connected to the 
sliding sleeve by links, the movement of the sleeve being transmitted to 
the second arm by the links to open or close the arms but, conversely, 
manual opening of the arms causing the sleeve to slide while compressing 
the spring. 
According to a further feature, the ejector comprises an electrical igniter 
triggering ejection, the igniter being fed by a pin embedded in an axial 
jack of the barrel, the functioning of the igniter being initiated by an 
electrical signal applied to the jack by a circuit of the submarine device 
.

Referring first to FIGS. 1 and 2, it will be seen that the cutter of the 
invention comprises an ejector 1 and a body 2 to which is fastened a first 
fixed arm 3, and on which is articulated a second mobile arm 4. 
The ejector 1 is a body of revolution comprising an electrical pin of 
revolution 5, the cylindrical seating of small diameter in which is lodged 
an electrical igniter 6 the input wires of which are connected to the 
wires of the pin 5, and a cylindrical seat of large diameter designed to 
receive one end 7 of the body 2. The ejector 1 is provided to be lodged in 
a barrel 8 (FIG. 3), the pin 5 being engaged in an axial jack (not shown) 
to connect the input wires of 6 to the output wires of a control circuit 
of a telecontrolled submarine device carrying the gun barrel 8. The outer 
surface of the ejector 1 is formed with two circular grooves, one in which 
is disposed a toroidal packing 9 providing for fluid-tightness between the 
gun barrel and the ejector while at the same time preventing the water 
from reaching the pin 5, and the other in which is disposed a tangent pin 
10 engaged in aperatures 70 and 71 of the gun barrel 8. The tangent pin 10 
prevents any movement of translation of the ejector 1 relative to barrel 
8, but does not prevent rotation of the ejector 1 in barrel 8. A pin 11 
engaged in an aperature formed in the wall of ejector 1, surrounding body 
2 and embedded in a blind aperature formed in body 2, serves to make the 
body 2 fast in the ejector 1. 
The seating of the igniter 6 communicates with that of the body 2 in such 
manner that functioning of the igniter 6 ejects the body 2 from the 
ejector 1, the pin 11 being sheared during ejection. 
The portion 7 of the body 2 contains in seats provided for this purpose two 
primary cells 12 and 13 adapted to be primed by sea water, the output 
wires 14 of which enter the interior of the body 2 passing through 
fluid-tight seals 15. The external surface of the portion 7 is formed with 
a groove in which is lodged a toroidal packing 16 providing for 
fluid-tightness between the inner surface of the ejector 1 and the inner 
portion 7 of body 2 at the same time preventing sea water from reaching 
the primary cells 12 and 13 for as long as ejection of the body 2 has not 
taken place. 
Provided within the body 2 is a fluid-tight compartment containing an 
electrical delay system, such as a delay line or an equivalent component 
(symbolically illustrated by the rectangle 17) a detonator 18, a 
pyrotechnical relay 19, microswitches or microcontacts 20 and a piston 21. 
In fact, the inner compartment of body 2 comprises a plurality of branches 
shown in FIG. 2 and in FIG. 6, which is a section taken along the line 
VI--VI of FIG. 2. It should also be noted that the body 2 is in fact in 
two parts, one 22 of generally cylindrical shape which comprises the 
portion 7, and the other 23 of prismatic shape -- these parts being 
connected by screws or bolts (not shown). The portion 22 comprises a 
cylindrical cavity in which the circuit 17 is lodged. The portion 23 
comprises, in the axis of ejector 1, an aperature in which is lodged the 
detonator 18, in the axis of the arm 3, an aperature in which is lodged 
the pyrotechnical relay 19, an oblique aperature 24 communicating with a 
cavity 25 where the microswitches 20 are lodged, said cavity 25 being 
produced by forming a hollow in the body and then sealing the hollow with 
a plate 26 fastened with part 23 by screws or bolts 27, and finally an 
aperature the axis of which is perpendicular to the plane defined by the 
axes of ejector 1 and arm 3, and in which the piston 21 is lodged. As FIG. 
6 shows, the piston 21 comprises a piston body entirely contained in the 
aperature 28 and the head 29 externally of aperature 28 and projecting 
relative to part 23. The aperature 28 debouches into the cavity 25. The 
piston 21 has, at the end adjacent to plate 26, a blind axial aperature in 
which is engaged a spring 30 bearing on plate 26 and urging piston 21 in 
such manner that the head of piston 21 projects externally from part 23. 
Urged by spring 30, piston 21 is arrested by a shoulder provided in its 
lateral surface and which comes into abutment at 31 with the end of a 
member 32 in which the pyrotechnical relay is disposed and which projects 
into the aperature 28. The body of piston 21 is insulated from the 
exterior by a diaphragm 33 the edges of which are wedged against 23 and a 
washer by a plug 34 screwed into part 23. The plug 34 is formed with a 
central aperature through which the head 29 is screwed into the body of 
piston 21 to apply the diaphragm by means of a washer on the body. The 
head 29 is formed with a circular groove 35 the purpose of which will be 
described later. The aperature 24 serves for passage of electrical wires 
between the microswitches 20, and on the one hand, the delay circuit 17, 
and on the other hand, the electrical detonator 18. 
Normally in air at normal atmospheric pressure, the pressure on the head 29 
is balanced by the internal pressure in the compartment of the body 2 and 
the spring 30 maintains the piston 21 in the position indicated in FIG. 6. 
When the cutter has descended to a pre-determined depth, the hydrostatic 
pressure applied on the head 29 becomes preponderant and the piston is 
depressed into the aperture 28 to adopt its working position. In the 
inoperative position, the body of piston 21 constitutes a screen between 
detonator 18 and pyrotechnical relay 19, preventing untimely functioning 
of detonator 18 being relayed by relay 19 towards the charge of the arm 3. 
This is one of the safety measures for preventing a surface explosion. In 
the operative position, the body 21, which is recessed at 36, permits the 
detonator 18 to excite the relay 19. In this case, the position of 21 is 
defined by a shoulder which comes into abutment at 37 against member 32. 
On the other hand, in the operative position, the end of piston 21 (close 
to 26) mechanically actuates the microswitches 20. This is a further 
safety measure. 
The active, fixed arm 3 (FIGS. 2 and 8) comprises two partially cylindrical 
portions 38 and 39 which are portions of hollow metal tubes connected to 
form a figure-eight shaped section eight. Secured in the tube 38, along 
the two generatrices, is a dihedral 40 which, in cross-section, forms a V 
extending into portion 38. The dihedral 40 is for example made from 
copper, i.e. from a dense material, and defines the hollow volume of the 
hollow charge between the wall of 39 and the dihedral 40. The volume 
enclosed between portion 38 and dihedral 40 is filled with explosive 41. 
At the end 42 of the arm 3 there are provided means for providing 
fluid-tightness of the space filled with explosive and of the space filled 
with air between 40 and 39. At the other end, the air space is also 
sealed, but the explosive space communicates via three ducts 43, 44 and 45 
with the outlet of the pyrotechnical relay 19, as shown in FIGS. 2 and 6. 
The lengths of the ducts 43, 44 and 45 are equal in such manner that the 
detonation initiated at 46, appears simultaneously at three coplanar 
points which are judiciously arranged, in such manner as to set up a plane 
detonation wave in the charge, this wave being displaced along the arm 3 
towards 42. 
The mobile arm 4 is a hollow tube mounted on a pair of plates 47 and 48, 
each disposed at one side of the body 2 and fastened with a pivot 49 
adapted to pivot in the element 23. At the end of the arm 4 there is 
provided an arresting plate 50 providing between 3 and 4 a free space and 
preventing the cable or the rod to be cut from escaping from the cutter 
when the latter is in the closure position, just before functioning 
thereof. 
FIG. 3 shows how the plate 48 is secured by a link 51 to a sleeve 52 
adapted to slide, without rotating, on the portion 22 of the body 2. More 
precisely, the link 51 is a rod having curved end 53 which is introduced 
into an aperture 54 in plate 48, and other curved end of which (of hook 
shape) is engaged in an aperture formed in a collar 55 fastened to the 
sleeve 52. The cutter also comprises a second link 62 similar to link 51, 
as shown in FIGS. 1 and 7. FIG. 4 shows a slot 56 and an aperture 57 
permitting engagement of the rod 51. It also shows that the outer surface 
of 22 is not entirely circular-cylindrical, but includes planar faces for 
preventing the rotation of sleeve 52 on body portion 22. 
FIG. 4 also shows that the gun barrel 8 comprises two pins 58 and 59 which 
are diametrically opposite relative to the axis of ejector 1 and are 
located in a plane including an angle of 45.degree. with the plane of the 
figure. The ends, cut along the line IV--IV (FIG. 3) of the pins 58 and 59 
are shown in FIG. 4. 
A spring 60 is compressed between the base 61 of the portion 22, the 
diameter of which is larger than that of the remainder of 22, and a face 
of the collar 55. The spring 60 tends to space collar 55 away from base 
61, i.e. to exert a pull on the links 51 and 62, thereby closing the 
cutter. The collar 55 has its edge notched at 63 and 64, the notches 63 
and 64 being diametrically opposite and in the form of arcs of a circle. 
The center of the notches 63 and 64 are at the same distance from the axis 
of ejector 1 as the axes of the pins 58 and 59, the radius thereof larger 
than that of the pins. Furthermore, there are recessed in the thickness of 
collar 55, namely recesses 65 and 66 which are also diametrically opposite 
but are offset through 90.degree. relative 63 and 64. The center of 65 and 
66 are at the same distance from the axis 1 as the axes of 58 and 59. 
It is recalled that the assembly of ejector 1 and body 2 is able to reotate 
in the barrel 8. The placing in operational position of the cutter is 
effected in the following manner: The cutter is opened, and the assembly 
of ejector 1 and body 2 is rotated in barrel 8 in such manner that the 
pins 58 and 59 pass respectively opposite 65 and 66, the collar 55 being 
spaced away from the barrel upon opening the arm 4. The spring 60 is 
tensioned, the assembly of ejector 1 and body 2 not being able to leave 
barrel 8, since it is maintained by pins 10 and 11. The pins or spindles 
maintain the collar 55 away from the barrel 8, thus maintaining opening of 
the cutter by the links 51 and 62. The hollow in the cups 65 and 66 
prevents any rotation of the cutter. On the other hand, in the inoperative 
position, with the assembly of ejector 1 and body 2 in the barrel 8, the 
cutter must be closed, this being achieved by passing the pins 58 and 59 
through the notches 63 and 64, thereby permitting the spring 60 to urge 
collar 55 which pulls the links 51 and 62 (i.e. 48 and 47), thereby 
closing the cutter. It should be noted that in order to pass from the 
closed inoperative position to the open position, it is necessary to 
manually open the arm 4 until the collar 55 is completely disengaged from 
the pins 58 and 59. Once recesses 65 and 66 are opposite the pins, this 
being obtained by rotating the assembly, the arm 4 is slightly released to 
engage the pins in 65 and 66, thereby preventing any subsequent 
unintentional rotation. 
FIG. 7 shows in greater detail the plate 47 and, in particular, the heel 67 
thereof. The plate 47 and its heel 67 have a thickness equal to or smaller 
than the width of the groove 35 formed in the head 29 of the piston 21. 
When the cutter is closed, the heel 67 is spaced away from the head 29 and 
leaves the latter free. When the cutter is open, the heel 67 is engaged in 
the groove 35 and prevents any movement of the piston 21. In fact, in the 
inoperative position of the cutter or when the latter is in storage (when 
it is normally closed) a clip 68 is engaged in the groove 35 to prevent 
any movement of the piston 21. Finally (as FIG. 6 shows) the head 29 is 
also protected against unintentional mechanical impacts by a protective 
lug 69 fixed by a screw or bolt to the portion 23. In FIG. 7, the open 
position of the cutter is indicated by the broken lines. 
FIG. 5 which corresponds to a section taken along the line V--V of FIG. 3, 
shows how the tangent pin 10 at the bottom of the groove in the ejector 1 
permits the assembly 1-2 to rotate in barrel 8, while preventing movements 
of translation. The sections of FIGS. 4 and 5 do not show in detail the 
interior of ejector 1 or body 2, which is already shown elsewhere. FIG. 5 
shows furthermore, the bases of the pins 58 and 59. In FIG. 4 pin 59 is 
shown in broken lines to render recess 66 visible, the opposite being true 
for pin 58 and recess 65, respectively. 
FIG. 9 is a block diagram illustrating the electrical wiring diagram and 
permitting a more ready understanding of specific phases of functioning of 
the cutter of the invention. There are again shown the primary cells 
12-13, the wires 14 comprising a wire 70 connected to the input of the 
delay circuit 17 and a wire 71 connected to a fixed contact of microswitch 
20.1, the detonator 18, the piston 21, the pyrotechnical relay 19, the 
charge 41 and the microswitches 20.1, 20.2 and 20.3. The output of delay 
circuit 17 is connected to a fixed contact of 20.3. The common terminal of 
delay circuit 17 is connected to a fixed contact of 20.2, which is 
connected by the wires 72 to the mobile contact of 20.1. The second fixed 
contacts of 20.2 and 20.3 are connected by a wire 73. The mobile contact 
of 20.2 is connected to an input of detonator 18, whereas the mobile 
contact of 20.3 is connected to the other input of detonator 18. In the 
inoperative position of the piston 21, the mobile contact of 20.1 (in its 
illustrated position) disconnects wire 71 from wire 72, thereby preventing 
application of any signal to the circuit 17. On the other hand, the mobile 
contacts of 20.2 and 20.3, with the wire 73, short circuit the input of 
the detonator 18. Thus, there are two safety systems in cascade, which 
prevent triggering of the detonator 18. Even if the latter is detonated, 
the piston 21 being inoperative, the mass present between detonator 18 and 
pyrotechnical relay 19 would prevent initiation of pyrotechnical relay 19 
and thus of explosive charge 41. Finally, it will be recalled that the 
piston is maintained in the inoperative position by the heel 67 of plate 
47 or the clip 68, and that it is protected by the lug 69. 
When the piston 21 passes into the operative position, it provides an empty 
space 36 between 18 and 19, and reverses the positions of the mobile 
contacts of 20.1, 20.2 and 20.3. 
A description will now be given of the various stages of preparation of use 
of the cutter. In the storage condition, the ejector 1 is mounted on the 
body 2, the arm 4 of the cutter is closed and the clip 68 locks the piston 
11. The spring 60, through the intermediary of the sliding sleeve and the 
links 51 and 62 brings the mobile arm into alignment with the active arm. 
In order to mount the cutter on the gun barrel 8 of a submarine device, the 
assembly 1-2 is engaged in the barrel 8, leaving the arm 4 closed and 
engaging the pins 58 and 59 in the notches 63 and 64. The pin 10 is 
inserted through the apertures of 8 and locks the assembly 1 and 2 in 
translation in 8. 
In order to cock the cutter, the mobile arm 4 is manually pivoted, thereby 
causing the sleeve 52 and the collar 55 to slide, through intermediary 
links 51 and 62, at the same time compressing the spring 60. Once the 
collar 55 has been freed from the pins 58, the assembly has rotated in the 
barrel (which remains fixed) through an angle of 90.degree. and, upon 
slightly releasing the arm 4, the pins are introduced into the recesses 65 
and 66, where they prevent the sleeve from returning to its inoperative 
position thus bringing about closure of the arms. The spring 60 is 
tensioned. The heel 67 of 47 locks the piston 21 and the clip 68 may be 
removed. 
The pivotable arm 4 and fixed arm 3 then define a sector which is 
preferably in a horizontal plane and in the field of a television camera 
mounted on the submarine device. 
The device is introduced into the water and guided by telecontrol towards 
the apparatus to be cut, which may be a cable, a buoy-rope, a rod, etc. 
When this apparatus is within the sector formed by the arms 3 and 4, a 
telecontrol order is supplied to a circuit of the submarine device which 
transmits it to the igniter 6 of the ejector 1 through the pin 5. The 
thrust of the gases produced ejects the body 2, cutting the pin 11, the 
ejector 1 remaining in the barrel 8. 
The collar 55 no longer bears on the pins 58 and 59 of 8. The spring 60 is 
detensioned and, through the intermediary links 51 and 62, the arm 4 is 
closed against the arm 3, enclosing the object to be cut. 
On reclosing, the arm 4 unlocks the piston 21 which, under the effect of a 
hydrostatic pressure, passes into the working position and changes the 
state of the contacts 20.1, 20.2 and 20.3. The inputs of the circuit 17 
are connected to the terminals of the primary cells 12 and 13 which, on 
ejection and only from that instant on, are primed by contact with the sea 
water. The detonator 18 is connected to the outputs of circuit 17. After 
the propagation delay of the signal applied by the primary cells to the 
circuit 17, through this same delay circuit 17, the detonator receives its 
signal 17. Said delay may be for example a 20 minute delay, thereby making 
it possible to recover the submarine device. 
The detonator 18 functions and excites through open passage 36 the 
pyrotechnical relay 19 which initiates the explosive charge 41, as stated 
herinabove. A planar explosive jet, normal to the direction of the arm 3, 
caused by the explosion of charge 41 is propogated from one end to the 
other of arm 3 and cuts any article situated between arms 3 and 4.