Ammunition and explosives – Miscellaneous
Reexamination Certificate
2000-01-21
2001-08-14
Jordan, Charles T. (Department: 3641)
Ammunition and explosives
Miscellaneous
C102S372000, C102S374000, C102S439000, C102S520000
Reexamination Certificate
active
06272997
ABSTRACT:
The present invention relates to a clip device for locating a fin stabilised projectile axially in the barrel of a launcher and preventing the projectile from slipping forwards when the muzzle of the barrel is depressed.
It is operationally desirable to fire the projectile at both relatively high angles of elevation and relatively low angles of depression of the barrel. Throughout the range of angles required for operation of the launcher it is necessary to ensure that the projectile is positioned such that the firing pin is able to reach and ignite the propellant charge. Our published patent application number WO93/07439 describes a breech loading mortar system having means for preventing a round of ammunition from slipping backwards after being loaded when the barrel is at a relatively high angle of elevation. Equally important is the need to prevent the projectile from sliding forwards after loading and prior to firing when the muzzle of the barrel is at a relatively low angle of depression.
Our European Patent EP0651224 which is incorporated herein by reference attempts to overcome the problems associated with projectiles sliding forwards in the barrel of a launcher at relatively low angles of depression of the barrel by disclosing a clip for retaining a round of ammunition in a desired position in the barrel of the launcher. This clip is cylindrical, with grooves extending in radial and axial directions, the grooves designed to engage the fins of a projectile. The clip and the round of ammunition are loaded together into the breech of the launcher, the engaged fins of the round of ammunition being prevented from sliding out of the grooves in the clip by the frictional resistance between the clip and the fins. The clip also has a rim extending circumferentially around its back edge, at the opposite axial end to the grooves, which is designed to allow the clip to engage with a recess at the breech end of the launcher to prevent forward movement of the clip. In this manner the round of ammunition is held in a desired position for firing and is not able to slide forward down the barrel of the launcher even at low angles of depression. The clip is made from a thermosetting plastics material which is hard, strong and rigid such that it can engage the fins and not deform under the intense heat and pressure of firing.
The clip disclosed in EP0651224 relies on the frictional forces between the walls of the grooves of the clip and the fins of the projectile being sufficient to prevent the projectile from sliding away from the clip and the firing pin at low angles of depression. Frictional forces rely on the material used for the fins and the clip as well as the tolerances of the fins and the grooves. If the fins are slightly thicker than desired they may not fit in the grooves of the clip, alternatively if the fins are slightly thinner than desired or the grooves slightly wider the frictional forces between the clip and the fins may not be sufficient to prevent the projectile from sliding away from the clip before or during firing. It is extremely difficult and expensive to ensure that each projectile has fins manufactured within a very narrow tolerance band suitable for producing an interference fit giving the necessary level of frictional resistance. Additionally, this clip may not be suitable for use over the range of angles generally demanded during launch. At low angles of elevation or low angles of depression, for example in the range +5 to −5 degrees to the horizontal, where increasingly greater frictional resistance is required to prevent the projectile from sliding, this clip can result in mis-firings where the projectile has slid away from the firing pin before firing. This is extremely dangerous in terms of operational efficiency and safety of personnel, as mis-fired projectiles may launch a considerable time after being fired, sometimes in the order of several minutes afterwards. Additionally, at higher angles of barrel elevation the clip may be itself inclined to slide backwards in the barrel if the frictional resistance between the clip and the barrel is not great enough, which can also result in mis-firings or blocking the breech.
It has also been found that when the breech is closed, the force of closing the breech can cause the projectile to be knocked out of the clip disclosed in EP0651224.
Dependence on an extremely tight interference fit to provide sufficient friction can be a serious drawback, due to the difficulties associated with consistently manufacturing fins and clips to the required tolerances, and can result in a higher than desirable number of mis-firings.
Additionally it has been found that the inflexible hard plastics material used may shatter when exposed to the extremely high pressure forces experienced during firing. The grooves in the clip encourage stresses to gather at the tips of the grooves, and if the material is hard and inflexible the clip may suddenly suffer catastrophic crack propagation and shatter under pressure forces. This is also a clearly undesirable aspect of a clip with regard to both safety and operational efficiency.
It is an object of the present invention therefore to provide a clip suitable for retaining a fin stabilised projectile in a desired position in a barrel of a launcher such that the projectile is prevented from sliding out of the firing position at angles of approximately −5 to +20 degrees, so resulting in a substantially lower number of misfires than hitherto achieved. It is a further object of the present invention to provide a reusable clip able to consistently withstand the pressure forces associated with firing without shattering or deforming so that it may be reliably re-used.
According to the present invention there is provided a clip for the retention of a fin stabilised projectile in a desired position in a barrel at the rear breech end of a launcher, the clip comprising a generally cylindrical body portion having:
engagement means for engaging with the launcher at the said rear breech end, said engagement means extending at least part of the way around the said cylindrical body portion and adapted to prevent forward movement of the clip when positioned in the launcher,
a substantially central axial aperture for allowing access for firing the projectile,
a plurality of radially and axially extending grooves for engaging the fins of the projectile when the clip is fitted to the projectile, each of said grooves having facing walls defining the groove therebetween, and the grooves adapted to divide the cylindrical body portion into a plurality of connected segments,
locating means positioned on at least one of said walls of at least one of said grooves and intruding into or above the groove, said locating means adapted to engage positively at least one of the fins of the projectile to prevent the projectile from readily slipping out of the clip when the clip is fitted to the projectile.
The locating means may comprise a locating flange which extends in a generally radial direction. The locating flange may extend along a substantial portion of the radial length of at least one of said walls of said grooves. The locating flange is preferably located at the axial end of the segments furthest from the rear breech end.
The axial lengths of the plurality of connected segments formed by the grooves may not all be the same, and in one embodiment of the invention circumferentially alternate segments are significantly longer in the axial direction than the intermediate segments. Each of the longer alternate segments may have a locating flange on at least one of said walls of said grooves at the axial end furthest from the rear breech end. The locating flange is thereby positioned over the space situated adjacent said longer alternate segments above the adjacent groove.
The axial end of the longer alternate segments furthest from the rear breech end preferably have tapered surfaces in the radial direction, such that the axial length of the longer alternate segments increases towards the axial cent
Hewkin Derrick
James David J
Chambers Troy
Jordan Charles T.
Nixon & Vanderhye P.C.
Royal Ordnance Plc
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