Base and obturating ring arrangement

An obturating arrangement for a gun barrel of the type having a right-angled obturating ring having its axially extending arm disposed within a recess in the base ring at the end of the gun barrel and its inwardly radially extending arm engaging, in a known manner, a breechblock wedge insert. In known arrangements of this type powder residues generated during firing, which may accumulate in the recess of the base ring and become lodged underneath the supporting face of the obturating ring arm projecting into the recess, may cause the basic play between the obturating ring and the breechblock wedge insert to be reduced, so that malfunctions during the closing of the breechblock wedge may occur. To overcome these drawbacks and also to increase operational reliability and lengthen the time between cleanings, the free end of the obturating ring arm projecting into the recess is arranged at a distance from the base surface of the recess while the rearwardly projecting end of the bead defining the inner wall of the recess is configured as a support for the obturating ring. The free end of the arm projecting into the recess preferably includes a sloped surface tapering toward the exterior of the obturating ring, and thus produces a stripping effect. Powder residues possibly still present in the enlarged volume of the recess can be blown out by fast flowing gases passing through a reduced opening between the bead end and the radially disposed arm.

BACKGROUND OF THE INVENTION 
The present invention relates to an obturating arrangement for the breech 
end of a barrel of a gun having a wedge type breechblock. More 
particularly the present invention relates to a base ring provided with a 
right-angled obturating ring having a first arm, which extends parallel to 
the longitudinal axis of the gun barrel, and thus of the base ring, 
projecting into a recess delimited by a bead of the base ring and, in 
order to provide obturation, having its exterior face lying against the 
outer axially extending abutment surface of the recess, and having a 
second arm, which is arranged at a right angle to the gun barrel and to 
the first arm, extending radially inwardly beyond said bead so that its 
exterior surface can lie against an insert of a breechblock wedge to 
provide obturation. 
Such an obturating ring arrangement is disclosed in the book, entitled 
"Handbook on Weaponry", published by Rheinmetall GmbH, Dusseldorf, 2nd 
English Edition, 1982, page 340, FIG. 862. 
The arm of this obturating ring which projects into a recess in the base 
ring is axially supported at the base surface of the recess. The bottom of 
the base ring is difficult to clean, and thus sometimes it is possibly 
insufficiently cleaned so that the powder residue generated by the firing 
of a round and deposited at the bottom of the base ring may creep 
underneath the supporting face of the arm and, in a disadvantageous 
manner, reduce the basic play of the obturating ring relative to the 
breechblock wedge. This can possibly compress the breechblock wedge before 
it reaches its final position and prevent it from performing a complete 
closing stroke. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to improve the obturating 
arrangement in the base ring such that the closing function is ensured to 
operate in a manner not susceptible to malfunctions. 
The above object is generally achieved according to the present invention 
by an obturating arrangement for the breech end of a barrel of a gun 
having a wedge type breechblock, with the arrangement including a base 
ring having an end surface with an annular recess whose inner wall is 
delimited by an axially extending bead and whose outer wall extends 
substantially parallel to a longitudinal axis of the ring, and a 
right-angled obturating ring having first and second arms whose respective 
exterior surfaces are flat and are substantially perpendicular, with the 
first arm extending into the recess and having its exterior surface 
abutting the outer surface of the recess, and with the second arm 
extending radially inwardly from the first arm beyond an outer end of the 
bead so that its exterior surface can lie against an insert of a wedge 
type breechblock to provide obturation; and wherein: the end of the bead 
is configured as an abutment for, and normally abuts, the second arm of 
the obturating ring, and the length of the first arm is such that a free 
end of the first arm is axially spaced from the base surface of the 
recess. 
According to the invention, the obturating ring is no longer supported on 
the sealing lip of the axially arranged arm at the bottom of the recess in 
the base ring. Rather its radially extending arm lies against the 
rearwardly projecting end of a bead of the base ring where it delimits the 
recess. 
During firing, this radial arm lays itself against the breechblock wedge 
insert in an obturating manner so that a minimum amount of basic play, for 
example 0.1 mm to 0.2 mm, appears in the interior between the radial arm 
and the end of the bead. During firing, the small amount of basic play 
between the bead and the radial arm causes the gas to take on a high 
velocity so that powder residues within the base ring recess are 
substantially blown away, and a self-cleaning effect is produced from 
round to round. 
The present invention further provides that the free end of the axially 
arranged arm of the obturating ring is spaced from the base surface of the 
recess. This enhances the self-cleaning effect and prevents jamming of the 
combustion residues in the recess underneath the end of the arm, so that 
axial displacement of the obturating ring in the direction of the 
breechblock wedge caused by powder residues is impossible. In an 
advantageous manner, the novel configuration of the obturating system 
according to the present invention makes the breechblock system immune to 
malfunctions to a great degree. 
Additionally, maintenance of the sealing system is simplified so that the 
number of rounds to be fired until the sealing system should be checked is 
increased considerably, and thus the operational reliability of the 
breechblock is also significantly improved. 
According to one feature, the arm end projecting into the recess, i.e, the 
axially arranged arm, is provided with a slope which tapers toward the 
exterior surface of the obturating ring so that this arm, due to its axial 
mobility within the basic play, acts as a dirt rejecter and thus excludes 
the accumulation of powder residues on the abutment surface of the recess. 
The distance between the lower free end of the sloped face of the 
obturating arm and the bottom of the recess is at least 1 mm. 
Additionally, a rounded configuration of the bottom of the recess provides 
a good self-cleaning effect. 
The present invention will be described in greater detail below with 
reference to an embodiment thereof that is illustrated in the drawing 
figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 illustrate the rear end of a gun barrel 12 and the obturating 
arrangement between a breechblock wedge 34, which is displaceable 
transversely to gun barrel 12 within a breech ring (not shown in detail). 
Gun barrel 12 is provided with an external thread 13 for fastening the 
breech ring and, at its rear end, with a recess 38 in its interior for 
accommodating a base ring 10 equipped with right-angled obturating ring 
16. The base ring 10 is fastened to the gun barrel 12 by means of screws 
42. 
FIG. 2 shows the breechblock wedge 34 in the closed position in which a 
breechblock wedge insert 36 constitutes the abutment face for the 
obturating ring 16 which is mounted in a recess 19 in the end surface of 
base ring 10. The detail marked III in FIG. 2 illustrates the prior art 
arrangement of the right-angled obturating ring 16 within base ring 10. 
The arm of obturating ring 16 disposed parallel to the longitudinal axis 
of gun barrel 12, and thus of the base ring 10, projects into a recess 19 
which is formed in the end surface of ring 10 and has its inner wall 28 
defined by a sloped inner surface of a bead 14 of base ring 10. The free 
end 15 of this arm is supported on the base surface 22 of the recess 19 
while its exterior surface lies against an axially extending abutment 
surface 30 defining the outer wall of recess 19. In order to provide 
obturation, the other arm of ring 16, i.e., the arm arranged at a right 
angle to gun barrel 12, extends radially inwardly beyond the free end of 
bead 14 so that its exterior surface, which forms a right angle with the 
exterior surface of the other axially extending arm, can lie against an 
insert 36 of breechblock wedge 34. 
In the conventional manner shown in FIG. 2, the depth of the recess 19 in 
base ring 10, which extends to base surface 22, is shorter than the length 
of the arm of obturating ring 16 disposed parallel to the axis of the gun 
barrel. A basic play of 0.1 mm to 0.2 mm required between the arm of 
obturating ring 16 extending radially to gun barrel 12 and breechblock 
wedge insert 36 in order to perform the transverse movements of the 
breechblock wedge 34 required to open and close the chamber in gun barrel 
12 can be set by displacing base ring 10 in the axial direction. 
A threaded ring 18 is provided for setting the axial play required between 
the radial arm of obturating ring 16 and the breechblock wedge insert 36. 
This threaded ring 18 faces gun barrel 12 and is supported on an abutment 
face 40 of recess 38. The ring 18 can be screwed axially into an annular 
groove within base ring 10. Such a ring 18 has already been disclosed in 
Federal Republic of Germany Patent Application Serial No. P 39 22 334.5 
corresponding to U.S. application Ser. No. 07/528,428, filed May 25th, 
1990, now U.S. Pat. No. 5,054,366 issued Oct. 18th, 1991. 
The bead 14 of base ring 10 includes a plurality of bores 24 shown in FIGS. 
1, 3 and 4 which connect recess 19, 20 and 21 respectively, with the 
chamber of gun barrel 12. Thus, when a shot is fired, obturating ring 16 
is charged with gas pressure directly in recess 19 via the bores 24. 
On its side facing the gun barrel chamber, base ring 10 ends in a narrow 
obturating lip 11 which lies against the interior surface of the gun 
barrel. The base ring 10 can easily be released out of recess 38 of gun 
barrel 12 by means of a plurality of forcing screws 44. 
In contrast to the conventional arrangement of the obturating system shown 
in FIG. 2, the obturating ring 16' according to the present invention, as 
shown in FIG. 3, when not stressed, no longer has the free end 15 of its 
axially parallel arm 16.1 normally resting on the base surface 23 or 32 of 
the recess 20 or 21, respectively, formed in the base ring 10. Rather, the 
relationship between the depth of the recess 20 or 21, the length of the 
arm 16.1 and the height of the end 26 of bead 14 are such that the 
interior surface of the radially extending arm 16.2 normally lies against 
the rearwardly projecting free end 26 of the bead 14 serving as a support. 
FIGS. 3 and 4 show the obturating ring 16' in a pressure charged position 
in which it lies against breech-block wedge insert 36 and is spaced, in 
contrast to the prior art comparatively large distance between the bead 
end 26 and the interior surface of radially extending arm 16.2, at a 
distance b which has been reduced to the value of the basic play of 0.1 mm 
to 0.2 mm. 
The free end 15 of arm 16.1 of obturating ring 16' where it projects into 
recess 20 or 21 is spaced from the base surface of the recess at a 
distance a which is at least 1 mm, and preferably 2 to 5 mm. 
The distance b, which is reduced to the basic play according to the present 
invention, now substantially prevents, compared to the above described 
prior art embodiments, the direct penetration of powder residues and, due 
to the already described advantageous effect of the high gas velocity 
during firing, produces a self-cleaning effect within recesses 20 and 21. 
Moreover, the free end 15 of arm 16.1 of obturating ring 16' where it 
projects into recess 20, 21 preferably is configured as a dirt stripper. 
For this purpose, the end 15 of the arm is given a sloped inner surface 17 
which is oriented toward the exterior surface of obturating ring 16'. This 
sloped surface 17 forms an angle .alpha. between 30.degree. and 60.degree. 
with the exterior surface of the arm 16.1, so that a good striping effect 
is produced for possibly existing powder residues. The accumulation of 
disadvantageous powder residues underneath the frontal or end surface of 
arm 16.1 is additionally avoided in that the distance a of the free end 15 
of obturating ring arm 16.1 from the base surfaces of recess 20 or 21 is 
more than 1 mm. The shape of the base surface may be flat as shown for 
surface 23 of FIG. 3 or have an outwardly rounded shape, i.e., base 
surface 32 of FIG. 4. In both cases, possibly existing powder residues at 
abutment surface 30 are stripped off by sloped surface 17 and are 
substantially blown away by the gases flowing in at a great velocity. The 
large dirt accumulation volume given by distance a between arm end 15 and 
base surface 23 ensures that long checking and cleaning intervals are 
sufficient. 
The invention now being fully described, it will be apparent to one of 
ordinary skill in the art that any changes and modifications can be made 
thereto without departing from the spirit or scope of the invention as set 
forth herein.