Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The invention relates to a percussion fuse supplying
a selected delay when the projectile containing it impacts
on its target~
The fuse is of ~he type in which a firing pln is
Eorced into contact with a detonator. Centrifugal retaining
members contained in the fusejblock the firing pin from
advancing towards the detonator until impact occurs. A
movable sleeve in the fuse holds the firing pin steady and
a biasing spring keeps the movable sleeve in its rearmost
position until impact.
In known types of percussion fuse, see for example
Swiss Patent 623,40&, a mechanicàl delay is provided so that
a projectile can penetrate as deeply as possible into the
target. A similar result is achieved in Swiss Patent 352,593
which discloses the use of a firing pin supported directly
by a relatively weak safety spring to hold it in the safety
position during flight. Because the spring is weak as soon
as the projectile using this type of fuse penetrates soft
earth or snow the deacceleration of the projectile is so
small that the forward movement of the firing pin occurs
at a slow speed and may result in miss-ignition.
The present application provides a percussion fuse
in which the firing pin is held back while the projectile
penetrates soft earth or snow and the delay mechanism start~
only when the projectile hits harder ground. The delay
mechanism is such that the firing pin impacts on the
detonator with a speed great enough to ensure reliable
detonation.
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The present invention provides the further feature
that should the detonator not be ignited the resulting dud
shell can be handled safely. These features are achieved
by providing a structure so that it is only the inertial
forces acting on the firing pin which provide the resulting
detonation.
The present invention relates to a percussion fuse
comprising a detonator, a firing pin receiving a longitudinally
extending safety bolt in a recess at its rearward end, a
movable sleeve, a spring having one end bearing against the
fuse casing and the other against the movable sleeve to bias
it rearwardly, centrifugal retaining members positioned in a
transverse recess in the firing pin adapted to abut on one side
a smooth surface of the safety bolt and on the other side a
shoulder formed on the movable sleeve, the movable sleeve and
the firing pin advancing together by the effect of inertial
forces, whereby on impact the movable sleeve advances by
compression of the spring, the centrigual retaining members
retract and the firing pin is forced into contact with the
detonator by inertial forces.
The distinction of the fuse according to this
invention from previously known fuses is in the use of a
substantially strong spring which causes the firing pin to
be held away from the detonator in the case of a dud shell.
The system can be used with an instantaneous fuse
detonator as well as a delayed action pyrotecnic delayed
fuse. In the latter case the fuse is provided with a device
to block the instantaneous fuse system.
A detailed example of the percussion fuse of this
invention will now be described in conjunction with the
following drawings in which
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~ Figure 1 is a longitudinal section of the fuse before
- ~ the firing of the projectile,
Figure 2 is the same section of the pe~rcussion fuse
after impact on the -target, and
ELgure 3 ;s the salne section of the f~lse showing
impact of the firing pin on the detonator.
The percussion fuse of the invention has a casing 10
having a bore 11 communicating with a channel 12. A slidable
detonator member 13 is positioned in channel 12 and, as shown
in Figures 2 and 3, contains~a detonator 14. The detonator
is of a known type consisting of a capsule of an ~mpact-
sensitive material. The capsule has an opening 17 through
which a firing pin 18 can puncture the detonator.
; The slidable detonator member 13 can be displaced
from its unarmed or safety position, in which the detonator
is outside the path of firing pin 18, to its armed or live
position in which detonator 14 is located in the path of
firing pin 18. Figure 1 shows the safety position and
Figures 2 and 3 the armed or live position. A movable sieeve
19 is located in bore 11 of housing 10. A shown in Figure l t
in the safety position of the slidable detonator member 13,
sleeve 19 has lts front end abutting against member 13 and
its other end abutting on a flange 20. Flange 20 is formed
with an internally extending bolt 21 and abuts on a shoulder
22 of bore 11, being retained in that position by inwardly
directed segments 23 of the casing~ Thus, movable sleeve 19
is secured against any displacement while the mechanism is
in the safety position. Once the slidable detonator member 13
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is in its armed or live position movable sleeve 19 can
advance against the return force of a strong spring 24 as
shown in Figures 2 and:3. In the furthest forward position
of sleeve 19 a shoulder 25 formed on it abuts on a ring 26
held in casing lO.
A displaceable firing pin 18 is located in sleeve 19
and has at its base a lengthwise bore to accommodate bolt 21
and a transverse bore to accommodate a pair of spherical
members 29. As shown in Figure 1 in the safety position of
slidable member 13 sleeve l9 is prevented from forward
movement by sphericai members 29 engaging an inwardly
directed circuIar shoulder 30. As can also be seen from
Figure 1 the sleeve canno-t move in the opposite direction
since it abuts against flange 20.
The center portion of firing pin 18 is formed with a
cylindrical shoulder 31 adapted to engage a corresponding
shoulder 32 formed in movable sleeve l9. The fuse is so
dimensioned that when the tip of the firing pin penetrates
detonator 14 shoulder 31 engages with shoulder 32.
The sequence of operation of the apparatus will now
1'. be described, The fuse is located in the head of a
projectile such as a shell or bullet and when the projectile
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is fired the slidable detonator member 13 is moved from its
safety position shown in Figure 1 to its armed or live
position as shown in Figures 2 and 3. This movement is
caused either by rotatlon o the projectlle or by a spring. ~ :~
During the flight of the projectile through the air before it
reaches its target movable sleeve 19 is held in its furthest
back position by the relatively strong spring 24. This,
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in turn, by reason of bolt 21 acting on spherical rnembers 29
prevents the firing pin 18 from moving forward. Thus, as lonq
as movable sleeve 19 is fully held back by the strength of
spring 24 the firing pin cannot move. When the projectile
impacts on its target the resulting retardation reaches an
amount at which the inertia of movable sleeve 19 and firing
pin 18 overcomes the force of spring 24 and moves forward. At
this stage the material force of firing pin 18 acts forwardly
on sleeve 19 by reason of members 29 engaging shoulders 30.
The delay in this forward movement occurring is proportional
to the force exerted by spring 24. Once movable sleeve 19
moves forward the firing pin is correspondingly free to move,
as spherical members 29 can move inwardly on contact with
shoulder 30 since the blocking action oE bolt 21 is now
removed. The firing pin is thus released to move forward
relatively to sleeve 19 and the tip impacts on detonator 14.
If, for any reason, detonator 1~ is not -then ignited
and the projectile retardation has ceased, spring 24 returns
movable sleeve 19 to its original position, that is referring
to E'igure 3, movable sleeve 19 can be pushed back a distance a,
The resulting movement is transferred from shoulder 32 of
sleeve 19 to shoulder 31 of the firing pin 18 which will
correspondlngly be retracted by the distance a. Thus, aftPr
; the effect of the lnertlal delay upon lmpact has flnished
firing pin 18 can no longer impact on detonator 14. Since a
relatively strong spring 24 is used to provide the required
impact delay~ even though the firing pin is no longer secured
by the spherical members 29 as shown in Figure 1, it is
nevertheless not able to penetrate the detonator and the fuse
is thus secured against misfire~
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