FR2575547A1 - Bullet-sealing system in cartridge case - Google Patents

Abstract

The system forms a sealed joint between the cartridge-case and bullet of a round of ammunition. The case is crimped against the bullet, and a coating of material polymerising under the effect of ultraviolet rays is deposited over the outside of case and bullet at the join. The material is then polymerised by ultraviolet rays. Deposition can be by a micro-dispenser, which can be held stationary while the round is rotated about its lengthwise axis.

Description

Method for obtaining a tight seal between the socket and the bullet of a cartridge.

The invention relates to a method for obtaining a leaktight seal between the socket and the bullet of a cartridge in order to avoid the humidification of the propellant powder contained in the socket.

In a known manufacturing process, the seal between the socket and the bullet of a cartridge is ensured by the combination of a deposit prior to the mounting of sealant in the socket and of the crimping of the cartridge.

Said deposit consists of a sealing varnish, for example bituminous varnish, deposited inside the mouth of the socket, this deposit being followed by drying of the socket by storage for eight days for example.

After this drying period, the sockets are loaded and provided with a ball, the required seal being obtained by crimping the cartridge.

This known manufacturing process has drawbacks.

In fact, it happens that, in certain cartridges, the loading conditions are such that the air trapped in the sleeve at the time of cartridge sealing creates an overpressure destroying the seal obtained by the layer of product deposited for this purpose in the sleeve.

To solve this problem, in current manufacturing methods, provision is made for additional storage of several days of cartridges obtained according to the known method mentioned above in order to allow stabilization of the internal pressure. In addition, this storage is followed by an additional deposit of a sealing varnish on the sleeve-ball joint of each cartridge.

A disadvantage of the method currently applied consists, a.e., in the fact that it is necessary to interrupt the manufacturing process several times, for example by storing the cartridges in order to obtain the required effects.

Another drawback of said method relates to the need to provide not only an interior varnish but also an exterior varnish and, additionally, soiled cartridges are obtained, which is mainly due to the use of melanoid and an exterior varnish.

In order to overcome these various drawbacks, a first object of the invention relates to the process for the manufacture of cartridges, making it possible to rationally obtain a perfect seal between the socket and the bullet, regardless of the loading conditions.

Other advantages obtained by the method according to the invention relate, a.e., the elimination of the deposit of bituminous varnish in the socket as well as the elimination of the storage of the cartridges.

The method according to the invention consists substantially in applying, after the crimping of the sleeve on the bale, a deposit of a layer of a polymerizing product with ultraviolet rays on the external contiguous parts of the sleeve and the bale and the exposure of said product to ultraviolet rays in order to obtain its polymerization.

In order to bring out more clearly the characteristics of the invention, the latter is described in more detail below, purely by way of example, and illustrated in the appended drawings in which:
Figure 1 is a view of the deposition of a polymer product
risant with ultraviolet rays on the socket joint
ball;
Figure 2 shows a view of the process during the
polymerization of said product;
FIG. 3 represents a cartridge obtained by the
process according to the invention.

The method according to the invention is substantially characterized in that a product polymerizing with ultraviolet rays is used, this product being deposited on the joint between the socket and the ball; this product is then subjected to ultraviolet rays in order to be polymerized.

The most suitable embodiment is as follows: the cartridge 1 is first loaded and crimped. The crimping action is carried out without the intervention of a sealing means and consists solely of tightening the mouth 2 of the socket 3 around the ball 4.

As shown in FIG. 1, immediately after the crimping operation, a layer 5 of a polymerizing product with ultraviolet rays is deposited on the joint 6 of the sleeve 3 and the ball 4, more specifically on the upper rim 7 of the socket 3. This is carried out, according to FIG. 1, by a microdosing device 8 in front of which the cartridge scrolls in rotation about its longitudinal axis.

The cartridges are, in this case, carried by a drum 10 forming, for example, part of the transfer station of a loading machine. Then, the layer S deposited on the joint 6 is exposed to ultraviolet rays in order to obtain the polymerization of the product of this layer 5 and to create, with great certainty, an assembly which is watertight to moisture between the socket 3 and the bullet 4. As shown in FIG. 2, this can be obtained by passing the cartridges 1 along a system or under a lamp with ultra-violet rays 11.

In order to fully expose the layer 5 to ultraviolet rays, the cartridges 1 can be carried by a rotary drum 12 in order to obtain that they execute a rotary movement such that the entire periphery of the layer 5 is presented towards the lamp ll I1 is obvious that one can use for this purpose, ea, a drum currently applied in known installations, for drying the identification varnish deposited on the tip of the ball.

Generally, the exposure time of layer 5 to ultraviolet rays - i.e. the polymerization time lasts only a few seconds and depends on the nature of the product used for layer 5.

In a variant not shown in the drawings, the cartridges may not be rotating on themselves, the microdosing device itself being driven by a rotary movement around the cartridge.

 It goes without saying that the method according to the invention can be combined with other methods known and used to produce, for example, a tight seal.

The main purpose of the invention is to produce a simple and effective seal between the socket 3 and the bullet 4 of a cartridge 1 by depositing a polymerizing product with ultraviolet rays and by exposure to ultraviolet rays, of the product deposited. It is therefore possible to carry out the design of the invention with a wide variety of devices, without departing from the scope of the invention.

Claims (6)

Claims 1.- Method for obtaining a leaktight seal between the socket and the bullet of a cartridge, characterized in that it consists substantially in crimping the socket (3) on the bullet (4); depositing a layer (5) of a polymerizing product with ultraviolet rays on the outer contiguous parts of the sleeve (3) and the ball (4) and exposing said product to ultraviolet rays in order to obtain its polymerization. 2.- Method according to claim 1, characterized in that the deposition of the layer (5) on the contiguous parts of the sleeve and the ball is carried out by means of a microdosuer (8). 3.- Method according to Claim 2, characterized in that the microdosing device (8) remains stationary while the cartridges (1) can be driven in rotation around their longitudinal axis during the deposition of the layer (5). 4.- Method according to claim 2, characterized in that the microdoser (8) can rotate around the longitudinal axis (9) of the cartridges (1) by depositing the layer (5). 5.- Method according to one of claims 1 to 4, characterized in that the deposition of the layer (5) on said contiguous parts is carried out while the cartridges are on the drum of a transfer station of a loading machine. 6.- Method according to one of the preceding claims, ca characterized in that the cartridges (1) are exposed to ultraviolet rays hang that they are on a drum provided for drying the identification varnish deposited on the tip of the ball.