US20100180757A1

US20100180757A1 - Method and apparatus for loading cartridges with pressable plastic bonded explosives

Info

Publication number: US20100180757A1
Application number: US12/476,675
Authority: US
Inventors: Jung-su Park; Hee-Duck Park; Hyoun-soo Kim; Tae-Soo Kwon
Original assignee: Agency for Defence Development
Current assignee: Agency for Defence Development
Priority date: 2009-01-19
Filing date: 2009-06-02
Publication date: 2010-07-22
Also published as: DE102009034039B4; KR101028813B1; KR20100084902A; DE102009034039A1

Abstract

Disclosed are an apparatus and method for loading small and medium caliber cartridges with pressable plastic bonded explosives (PBXs). A plurality of pellets are pre-formed to have a high density, and are loaded into a small and medium caliber cartridge one by one. Accordingly, a high and uniform density is obtained. And, when manufacturing small and medium caliber cartridges, the pressable PBXs are anticipated to be massively loaded into the small and medium caliber cartridges in the future.

Description

RELATED APPLICATION

The present disclosure relates to subject matter contained in priority Korean Application No. 10-2009-0004285, filed on Jan. 19, 2009, which is herein expressly incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a method and apparatus for loading cartridges with pressable plastic bonded explosives.
2. Background of the Invention
Generally, ammunition is loaded with high explosives, and provides lethal effects due to fragmentation and detonation occurring from an explosive energy of the high explosives. Methods for loading high explosives into weapon systems may be classified into a melting method for loading explosives in a melting manner, a casting method for loading explosives after stirring the explosives in a container, and a pressing method for loading explosives by mechanically processing raw material explosives in correspondence to shapes of weapon systems after compression-molding the raw material explosives with a high pressure. Based on the loading methods, the explosives have developed by being categorized into melt-loading type of explosives, castable explosives, pressable explosives, etc.
Ammunition weapon systems are massively produced. Accordingly, as explosives applied to the ammunition weapon systems, preferably used are explosives having low costs and easy loading characteristics even if they have a degraded function and high sensitivity. Representative explosives applied to the ammunition weapon systems include TNT, Composition B (Comp B), Composition A5 (Composition A5), etc., which are referred to as ‘the conventional explosives’. Here, the TNT and Comp B are melt-loading type of explosives, and are mainly used to the conventional ammunition due to easy loading characteristics into ammunition under a melted status in a container.
However, when the conventional TNT and Composition B undergo a phase transition from a melted status to a solid status, the following problems occur. Firstly, a shrinkage phenomenon occurs. Secondly, the TNT and Composition B have non-uniform densities, vulnerable mechanical properties, and high sensitivity to external stimuli. Accordingly, unpredictable detonation accidents may occur when dealing with the TNT and Composition B.
The Comp A5 is a granular explosive formed by coating RDX with stearic acid, and is mainly loaded into large ammunition in a pressable molding manner. The Composition A5 is mainly applied to the conventional ammunition due to its low costs. However, the Comp A5 has inferior storage characteristics due to leakage at a temperature more than 71° C., and may have crack occurrence therein when stored for a long time. Furthermore, the Comp A5 has high sensitivity to heat, and inferior molding characteristics.
Even if the explosives applied to the ammunition weapon systems have advantages such as easy loading characteristics and low costs, they are too sensitive to external stimuli to be easily handled. Furthermore, the explosives have inferior mechanical properties or storage characteristics.
The present invention is to solve the conventional problems such as an inferior loading density, and unexpected accidents occurring when directly loading high explosive powder into a cartridge body.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a method and apparatus for loading cartridges with pressable plastic bonded explosives (PBXs) capable of uniformly loading pressable PBXs into a cartridge body with a high density and capable of enhancing stability.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for loading cartridges with pressable plastic bonded explosives (PBXs), comprising: forming pellets by compression-molding pressable PBX powder into a size small enough to be accommodated in a cartridge body; and inserting the pellets into the cartridge body, and loading the pellets with compression. The cartridges have a high function and enhanced operational stability, and are massively manufactured.
In the step of loading pellets, a plurality of pellets are inserted into the cartridge body one by one, and then are compressed.
The cartridge may have a plurality of notch grooves on an inner wall of the cartridge body.
A pressure may be applied into the cartridge body and the notch grooves such that the pellets are loaded thereinto in the form of re-molded ones.
Here, the pellets may be inserted into the cartridge body irrespective of a direction of the notch grooves.
The step of forming pellets may comprise putting pressable PBX powder into a die; maintaining a pressure inside the die as a vacuum status; and continuously applying a predetermined pressure into the pressable PBX powder put into the die for a predetermined time by a punch.
The step of loading pellets may comprise fixing the cartridge body into a die; inserting pellets into the cartridge body; maintaining an inner pressure of the cartridge body as a vacuum status; and continuously applying a predetermined pressure into the pellets inserted into the cartridge body for a predetermined time by a punch.
Here, the pressure applied to the pellets may be set to be equal to that applied to the pressable PBX powder.
Here, each of the pellets may be formed in a cylindrical shape such that its length is longer than its diameter.
In the present invention, there is provided a cartridge including a cartridge body, wherein a plurality of notch grooves are formed on a wall of an inner space of the cartridge body, and pellets made from the pressable PBX powder are loaded into the cartridge body and the notch grooves with compression.
The present invention has the following advantages.
Firstly, according to the method and apparatus for loading cartridges with pressable plastic bonded explosives (PBXs) and cartridges manufactured thereby, the pellets (P) pre-formed to have a high density are loaded into the cartridge body one by one. Accordingly, the PBX may be uniformly loaded into the cartridge body with a high density, and a great amount of cartridges having a high function may be massively manufactured with less risk.
Secondly, the present invention may be easily applied to massively produce small and medium caliber cartridges. In the case of massively producing cartridges having a complicated inner structure, a loading density test for explosives can be easily and precisely performed through density measurement for molded pellets without a complicated process for calculating a volume inside the cartridge body. This may allow the present invention to be effectively utilized in quality managing aspects.
In the present invention, the cartridge body is provided with the notch grooves therein so as to easily generate fragmentation. Explosives of a high density are uniformly loaded into the notch grooves, thereby representing an excellent fragmentation characteristic. Furthermore, a non-uniform density or inner defects resulting in unpredictable detonation of the explosives do not occur, thereby enhancing operational stability.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a perspective view showing a cartridge according to the present invention;

FIG. 2 is a sectional view schematically showing a pellet forming unit for forming pressed plastic bonded explosives (PBXs) pellets of a high-density according to the present invention;

FIG. 3 is a perspective view showing a unitary pellet formed by the pellet forming unit of FIG. 2;

FIG. 4 is a sectional view schematically showing a pellet loading unit according to the present invention;

FIGS. 5A to 5C are operational state views sequentially showing a method for loading pellets into a cartridge body by the pellet loading unit according to the present invention; and

FIG. 6 is a perspective view showing a cartridge loaded with pellets according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Description will now be given in detail of the present invention, with reference to the accompanying drawings.
Hereinafter, a method and apparatus for loading cartridges with pressable plastic bonded explosives (PBXs) and cartridges manufactured thereby according to the present invention will be explained in more detail with reference to the attached drawings.
FIG. 1 is a perspective view showing a cartridge according to the present invention. More concretely, FIG. 1 shows a shape of a small and medium caliber cartridge loaded with explosives according to the present invention. The cartridge 1 has a warhead shape, and includes a cartridge body 2 formed to be decomposed into fragmentation by detonation of the explosives loaded therein.
The cartridge body 2 is provided with an inner space 3 for loading explosives therein. And, a plurality of notch grooves 4 are formed on a wall of the inner space 3 of the cartridge body 2 so as to facilitate fragmentation of the cartridge body 2. It may be very disadvantageous to compression-mold pressable PBX in the cartridge body 2 of which length is longer than its diameter, the cartridge body 2 having the notch grooves 4 and the inner space 3. Accordingly, a pressable granular PBX powder is compression-molded in a cylindrical shape having a ratio of 1:1 between a length and a diameter. So as to obtain stability and high molding characteristics with reduced friction, an inner wall of a die may undergo a surface process after a precision processing. However, it will not be easy to directly mold pressable granular PBX in the small and medium caliber cartridge 1. For instance, when the pressable granular PBX undergoes a direct compression molding in the cartridge body 2, an inferior density and detonation may occur.
In order to load the small and medium caliber cartridge where a direct compression-molding is impossible in the conventional art, with a pressable PBX with a uniform density, pellets pre-formed to have a high density (refer to FIG. 3) may be applied to the cartridge body 2 one by one. This method for loading the small and medium caliber cartridge with the pellets of a high density one by one is very advantageous in the aspects of a high molding density, a uniform density inside the cartridge body 2, stability in a molding process, and a massive productivity in a loading process. Compression-molded pellets may implement a density close to a theoretical maximum density (TMD) only if molding conditions are satisfied, and ensure a uniform density. By using the pre-formed pellets (P), the pressable PBX may be loaded with a uniform and high density, into the cartridge body 2 having the notch grooves 4 therein and having a length longer than a diameter. Furthermore, the pressable PBX may be also loaded into the notch grooves 4 without cavities. Using the pellets (P) may prevent the conventional problem that severe friction occurs between granular explosive powder directly loaded into the cartridge body and the notch grooves, thereby enhancing stability in a molding process. The process of pre-forming the pellets (P) can be easily implemented due to simple conditions, thereby being easily applied to a massive production for cartridges.
The method for manufacturing the cartridge 1 using the pellets (P) may comprise forming the pellets (P) by compression-molding pressable PBX powder into a size small enough to be accommodated in the cartridge body 2, and inserting the pellets (P) into the cartridge body 2, and loading the pellets (P) with compression. The steps will be explained based on FIGS. 2 and 4, respectively.
FIG. 2 is a sectional view schematically showing a pellet forming unit for forming pellets (P) of a high-density according to the present invention.
The pellet forming unit 10 includes a die 11, an upper punch 13, a vacuum line 14 for maintaining an inner pressure of the die 11 as a vacuum status, a lower ram 12, and pressable PBX powder for forming the pellets (P).
The die 11 is formed to have a negative shape of the pellets (P) together with the lower ram 12. The pellets (P) are formed to have a desired density and size by putting pressable PBX powder into the die 11 and then compressing the pressable PBX powder through the upper punch 13.
A process for forming the pellets (P) of a high density will be explained.
Firstly, a pressable granular PBX is put into the die 11 of the pellet forming unit 10 of FIG. 2. Next, the upper punch 13 is assembled with the die 11, and then a vacuum pump is driven to maintain an inner pressure of the die 11 as a vacuum status more than 740 mmHg. Once the die 11 maintains a vacuum status more than 740 mmHg, a pressure of 25000 psi is applied to the upper punch 13 for 30 seconds. The upper punch 13 applied with the pressure performs a compression-molding of the pressable granular PBX put in the die 11 into the pellets (P). Once the compression-molding is completed, the pellets (P) are separated from the die 11. Table 1 shows examples of each measured density of the molded pellets according to the present invention. It was observed that each of the molded pellets (P) has a high density.

TABLE 1

Density of molded pellets

	Theoretical	Measured
	Density (TMD,	Density
No.	g/cc)	(g/cc)	TMD (%)

1	1.763	1.756	99.6
2	1.763	1.759	99.8
3	1.763	1.755	99.5
4	1.763	1.756	99.6
5	1.763	1.752	99.4
6	1.763	1.756	99.6
7	1.763	1.752	99.4

FIG. 3 is a perspective view showing a unitary pellet formed by the pellet forming unit of FIG. 2. More concretely, FIG. 3 shows a pellet (P) pre-formed to have a high density. The pellet (P) of FIG. 3 is pre-formed to have a length a little longer than a diameter, which does not influence on the entire molding characteristic. Accordingly, the pellet (P) having a cylindrical shape may be configured to have a length a little longer than a diameter, thereby minimizing the number of the pellets (P) loaded into the cartridge body 2.
FIG. 4 is a sectional view schematically showing a pellet loading unit according to the present invention.
Referring to FIG. 4, the pellet loading unit 20 includes a die 21 for fixing the cartridge body 2, an upper punch 25 for pressurizing the pellets (P), a vacuum line 26 for maintaining an inner pressure of the die 21 as a vacuum status, a pneumatic lifting device 22 for lifting the cartridge body 2 upon completion of the PBX loading, and thereby ejecting the cartridge body 2 from the die 21, an upper punch guide 23, an impact damping device 24, the cartridge body 2 of the small and medium caliber cartridge 1, and the pellets (P).
FIGS. 5A to 5C are operational state views sequentially showing a method for loading the pellets (P) into the cartridge body by the pellet loading unit according to the present invention. FIG. 5 shows a method for loading three pellets (P), in which FIG. 5A shows a loaded status of a first pellet, FIG. 5B shows a loaded status of a second pellet, and FIG. 5C shows a loaded status of a third pellet.
A process for sequentially loading three pellets (P) into the small and medium caliber cartridge 1 will be explained as follows. Firstly, the cartridge body 2 is fixed to the die 21 of the pellet loading unit 20. Then, a first pellet (P) is put into the cartridge body 2. Once the upper punch 25 is downwardly moved to a preset position inside the die 21, a vacuum pump is operated to maintain an inner pressure of the die 21 as a vacuum status more than 740 mmHg. The vacuum status inside the die 21 is maintained until the first pellet (P) is completely loaded into the cartridge body 2. When a molding pressure of 25000 psi is applied to the upper punch 25 for one minute, the first pellet (P) is filled into the notch grooves 4 and a lower part of the hemispherical cartridge body 2 with an excellent bonded state. Here, the molding pressure of 25000 psi is equal to the pressure when pre-forming the pellets (P). Filling the pellets (P) into the notch grooves 4 and the lower part of the hemispherical cartridge body 2 results from suitable utilization of mechanical properties of the pressable PBX. The pressable PBX has a mechanical property of strong flexibility. When the same pressure as the pressure applied to pre-form the pellet (P) is applied to the upper punch 25, the pellet (P) having not restricted in the cartridge body 2 undergoes transformation. And, the pellet (P) is filled into a lower part of the notch grooves 4 and the hemispherical cartridge body 2. At the same time, the pellet (P) is completely bonded to the notch grooves 4 and a wall surface of the cartridge body 2 in the form of a re-molded one due to the pressure of 25000 psi. When a bonded status between the pellet (P) and the notch grooves 4 and the wall surface of the cartridge body 2 is excellent, operation stability of the cartridge 1 is enhanced.
In the present invention, the pellets (P) having a high density are filled into an empty space inside the cartridge body 2 by using mechanical properties of the pressable PBX, and are bonded to the notch grooves 4 and the wall surface of the cartridge body 2. This may prevent the conventional severe friction occurring when high granular explosive powder undergoes a phase change into a solid status from a granular status at the time of being directly compression-molded in the cartridge body 2, thereby enhancing stability in a loading process. Furthermore, since the density of the pellets (P) is high and uniform, pressable PBX is uniformly loaded into the entire part of the hemispherical cartridge body 2 including the notch grooves 4 with a high density. This may prevent a non-uniform density occurring when directly loading high explosive powder into the cartridge body 2. The uniform density plays a very important role to enhance a function of the pressable PBX and to solve high vulnerability of the pressable PBX. Once the pressable PBX is uniformly loaded into the notch grooves with a high density, a function for generating fragmentation of the cartridge body 2 is more enhanced, and detonation due to high vulnerability such as cavities or cracks in the pressable PBX resulting from a non-uniform density is prevented.
Once the first pellet (P) is completely loaded into the cartridge body 2 by a pressure for one minute, a vacuum status inside the cartridge body 2 is released, and then the upper punch 25 is restored to the initial status. In the same manner as the first pellet (P), the second pellet (P) is inserted into the cartridge body 2, and then is compression-molded. Upon completion of loading of the second pellet (P), the third pellet (P) is inserted into the cartridge body 2 for loading. When the third pellet (P) is completely loaded, the upper punch 25 is separated from the die 21. Next, the cartridge body 2 inside the die 21 is lifted by using the pneumatic lifting device 22. Then, the cartridge body 2 is ejected from the die 21, thereby completing the loading of the cartridge 1 with the pressable PBX.
FIG. 6 is a perspective view showing a cartridge loaded with pellets (P) according to the present invention. FIG. 6 shows a status that the small and medium caliber cartridge is loaded with a plurality of pellets (P) one by one. Referring to FIG. 6, the pellets (P) are uniformly loaded into the notch grooves 4.
In order to load the small and medium caliber cartridge where a direct compression-molding is impossible in the cartridge body, with pressable PBX with a uniform density, has been provided a method for loading the cartridge body 2 with pellets pre-formed to have a high density one by one. This method for loading the small and medium caliber cartridge with the pellets having a high density one by one is very advantageous in the aspects of a high molding density, a uniform density inside the cartridge body, stability in a molding process, and a massive productivity in a loading process. Compression-molded pellets may implement a density close to a theoretical maximum density (TMD) only if molding conditions are satisfied, and ensure a uniform density. The pellets (P) may be uniformly loaded into the cartridge body 2 with a high density even if the cartridge body 2 is provided with the notch grooves 4 therein and has its length longer than its diameter. Furthermore, the pellets (P) may be loaded into the notch grooves 4 without any cavities. Using the pellets (P) may prevent the conventional problem that severe friction occurs between high explosive powder directly loaded into the cartridge body 2 and the notch grooves 4, thereby enhancing stability in a molding process. The process of pre-forming the pellets (P) can be easily applied to a massive production for cartridges due to simple molding conditions.
The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present disclosure. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments.
As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.

Claims

1. A method for loading cartridges with pressable plastic bonded explosives (PBXs), comprising:

forming pellets by compression-molding pressable PBX powder into a size small enough to be accommodated in a cartridge body; and

inserting the pellets into the cartridge body, and loading the pellets with compression.

2. The method of claim 1, wherein in the step of loading pellets, a plurality of pellets are inserted into the cartridge body one by one, and then compressed.

3. The method of claim 1, further comprising forming a plurality of notch grooves on an inner wall of the cartridge body.

4. The method of claim 3, wherein a pressure is applied to inside of the cartridge body and the notch grooves such that the pellets are loaded thereinto in the form of re-molded ones.

5. The method of claim 3, wherein the pressable PBX is loaded under a status that an insertion direction of the pellets is irrespective of the notch grooves.

6. The method of claim 1, wherein the step of forming pellets comprises:

putting pressable plastic bonded explosives (PBXs) powder into a die;

maintaining a pressure inside the die as a vacuum status; and

continuously applying a predetermined pressure into the pressable PBX powder put into the die for a predetermined time by a punch.

7. The method of claim 1, wherein the step of loading pellets comprises:

fixing the cartridge body into a die;

inserting pellets into the cartridge body;

maintaining an inner pressure of the cartridge body as a vacuum status; and

continuously applying a predetermined pressure into the pellets for a predetermined time by a punch.

8. The method of claim 7, wherein the pressure applied to the pellets is set to be equal to that applied to the pressable PBX powder.

9. The method of claim 1, wherein each of the pellets is formed in a cylindrical shape such that its length is longer than its diameter.

10. An apparatus for manufacturing cartridges, comprising:

a pellet forming unit for forming pellets by compression-molding pressable plastic bonded explosives (PBXs) powder into a size small enough to be accommodated in a cartridge body; and

a pellet loading unit for loading the pellets inserted into the cartridge body with compression.

11. The apparatus of claim 10, wherein the pellet forming unit comprises:

a die having a negative shape of the pellets;

a vacuum line for maintaining an inner pressure of the die as a vacuum status; and

a punch for applying a predetermined pressure to the pellets.

12. The apparatus of claim 10, wherein the pellet loading unit comprises:

a die for fixing the cartridge body;

a vacuum line for maintaining an inner pressure of the cartridge body as a vacuum status; and

a punch for continuously applying a predetermined pressure to the pellets inserted into the cartridge body for a predetermined time.