Patent Grant
8186274
Not Applicable
Not Applicable.
Not Applicable
1. Field of the Invention
This invention relates to the field of propellant gas delivery systems. More specifically, the invention comprises an improved energy delivery cartridge with a burst cup that allows controlled discharge of the propellant gases generated within said cartridge. The invention further comprises a method for forming said improved energy delivery cartridge during an assembly process.
2. Description of the Related Art
Although the present invention can be applied to any application requiring the use of metered propellant gases, it was primarily developed as part of a propellant system for launching 40 mm grenades (such as the U.S. Army's M433). The invention is an improvement to a prior design reduced to practice by the same inventor. The prior design is disclosed and claimed in U.S. Pat. No. 7,004,074 to Van Stratum (2006), which is hereby expressly incorporated by reference.
Metallic cartridges have been used to encapsulate solid propellants for many years. In recent years other materials have been substituted for the traditional brass, but the principles of operation remain the same: A projectile is seated in the open mouth of a cartridge case containing solid propellant. Ignition of the propellant is provided by percussive or electrical means. The burning propellant generates pressurized gas which forces the projectile out of the mouth of the case and then typically through a barrel bore.
The launching of a 40 mm grenade involves the same principles. The main difference, however, is the size and mass of the projectile. A typical shoulder-fired military weapon launches a projectile weighing less than 30 grams at a relatively high velocity (700-1,000 meters per second). In contrast, a 40 mm grenade weapon launches a projectile weighing over 200 grams at a relatively low velocity (70-80 meters per second). Thus, while the operating principles between the two types of weapons are the same, they can be said to operate in different regimes.
Since the human operator can only withstand a fixed amount of recoil, one cannot merely scale up the cartridge of a shoulder-fired rifle and create a useable weapon for launching 40 mm grenades. The design considerations are different. The incorporated U.S. Pat. No. 7,004,074 illustrates and describes an effective approach to the problem of launching large masses at low velocities. The '074 invention uses a high-pressure cartridge embedded within a low-pressure larger cartridge. A burst cup metering system is used to meter propellant gases from the high pressure cartridge into the low pressure cartridge, thereby accelerating the projectile in a smooth and controlled fashion. This approach helps to reduce the peak recoil loads experienced by a user. The high pressure found within the high pressure cartridge also ensures the reliable ignition and combustion of the propellant it contains.
The present invention seeks to simplify the construction and assembly of a suitable High-Low gas pressure cartridge. Although the illustrations and descriptions pertain to 40 mm grenade launchers, the reader should bear in mind that the invention applies to many fields beyond military munitions. A good example is disclosed in U.S. Pat. No. 6,189,926 to Smith (2001), which uses a High-Low pressure cartridge to inflate an airbag. Additional applications would include, without limitation:
1. Turbine and piston engine starters;
2. Parachute inflation devices;
3. Mechanical deployment device;
4. Life vest inflation devices;
5. Life boat inflation devices; and
6. Explosive bolt cutting devices.
The present invention is a modified fluid delivery cartridge.
The neck in the high pressure cartridge wall is preferably created when the high pressure cartridge is pressed into the low pressure cartridge. The high pressure cartridge wall actually starts as a conventional straight wall. As the high pressure cartridge is pressed into the low pressure cartridge, step 44 actually creates the neck in the high pressure cartridge wall.
The high pressure cartridge is preferably closed via a burst cup 46. The high pressure cartridge contains a quantity of propellant 36, which is ignited by striking percussion primer 34. Thus, the burst cup divides the assembly into high pressure chamber 31 (within the high pressure cartridge) and low pressure chamber 30 (the enclosure formed by base 24, low pressure cartridge wall 38, and projectile base 40). When the percussion primer is struck, it ignites the propellants within the high pressure cartridge and ruptures burst cup 46. The burst cup then forms an expansion nozzle which meters the hot propellant gases from the high pressure chamber into the low pressure chamber.
Turning briefly to
The assembly shown in
The inner charge casing wall, the step, and the charge vent hole preferably act as a sort of forming die when the high pressure cartridge is placed into the low pressure cartridge.
In
Looking still at
When the high pressure cartridge case is detonated, the burst cup ruptures and meters the propellant gases into the low pressure chamber.
Although the neck is preferably formed when the high pressure cartridge is inserted into the low pressure cartridge, this is by no mean the invention's only embodiment. The neck could obviously be formed in a separate die and the formed case could then be inserted into the high pressure case receiver. The function of the completed device would then be the same.
The amount of gas volume contained within the low pressure chamber prior to ignition of the high pressure cartridge has a significant impact on the recoil forces generated.
Greater volume tends to prevent a rapid rise in pressure within the low pressure chamber, which in turn tends to spread the recoil forces generated out over a longer period of time. Of course, the low pressure chamber volume enlarges once the projectile starts moving down the bore. However, rifling ring 36 largely seals the gap between the projectile and the bore, so that the projectile acts like a gas-driven piston.
The presence of a large volume in the low pressure chamber prior to the point where the projectile begins to move tends to act as an energy absorber which prevents a rapid spike in gas pressure. This will tend to reduce the peak low pressure chamber pressure experienced during firing. This reduction in peak low pressure chamber pressure will also reduce peak recoil forces experienced by the person firing the weapon.
The area under each curve represents the impulse imparted to each projectile. The area under each curve is very nearly equal, which must be true if the two projectiles are to achieve the same muzzle velocity (which is true for the test). However, the reader will observe that the peak recoil load for the high volume test is significantly lower. The recoil forces are also experienced over a longer period of time. In subjective terms, the use of a larger free volume in the low pressure chamber has taken a sharp jab and converted it into a longer shove. This shift makes the recoil forces much more tolerable for the shooter.
Although the preceding description contains significant detail, it should not be construed as limiting the scope of the invention but rather as providing illustrations of the preferred embodiment of the invention. Thus, the scope of the invention should be fixed by the following claims, rather than by the examples given.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3728967 | Hinkle et al. | Apr 1973 | A |
| 3771451 | Woodring | Nov 1973 | A |
| 3861309 | Veber | Jan 1975 | A |
| 3983817 | Tucker | Oct 1976 | A |
| 7004074 | Van Stratum | Feb 2006 | B2 |
| 7793591 | Van Stratum | Sep 2010 | B1 |
| 7802520 | Van Stratum | Sep 2010 | B2 |
| 7841279 | Reynolds et al. | Nov 2010 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20100147177 A1 | Jun 2010 | US |
