Hollow gunpowder column forming mold and forming method

Abstract

The hollow gunpowder column forming mold comprises a mandrel used for forming an inner hole of a gunpowder column, a mold sleeve used for forming the outer contour of the gunpowder column, an upper mold core assembly, a lower mold core assembly used for applying pressure and a demolding assembly used for achieving demolding. The mandrel and the die sleeve assembly are coaxially arranged to form a die cavity for containing powder; and the die sleeve is provided with an exhaust structure communicated with the die cavity. In the pressing process, air among loose powder particles in the die cavity is extruded and exhausted, and the air is guided out of the die through the exhaust structure, communicated with the die cavity, on the die sleeve, so that the air is prevented from being retained in the powder.

Description

Technical Field

[0001] This invention relates to the field of gunpowder pellet forming, specifically to a hollow gunpowder pellet forming mold and forming method. Background Technology

[0002] In the field of weaponry and equipment, ignition devices are key components for achieving ammunition ignition and detonation. Hollow propellant charges, as the core energy output element of ignition devices, directly determine the ignition reliability, energy release stability, and service life of the ignition device through their molding quality. Currently, the manufacturing process of hollow propellant charges for ignition devices generally employs "powder pressing" technology. This involves first mixing boron powder, potassium nitrate, and potassium perchlorate in a specific ratio, then adding a PVB solution (polyvinyl butyral solution) for granulation, followed by the external mixing of PVB powder (polyvinyl butyral powder) to adjust the powder's flowability and adhesion. Finally, the mixed powder is loaded into a mold and pressed into a hollow cylindrical structure using a press.

[0003] Existing molds generally use simple straight-line vents or no dedicated venting structure. However, the powder in hollow propellant columns is a multi-component mixture with numerous voids between particles. During compression, the powder is squeezed and the air in these voids is rapidly expelled. Because the venting path of straight-line vents is short and easily blocked by the powder, or because the vent positions do not correspond to the "gas accumulation zone" during powder compression, gas cannot be expelled from the mold cavity in time, leading to bubbles, looseness, or delamination defects inside the propellant column. On one hand, the PVB powder in the propellant has a certain viscosity, easily adhering to the inner wall of the vents during compression, gradually blocking the venting channels. On the other hand, hollow propellant columns have a "hollow thin-walled" structure, with a thin distribution of powder around the mandrel. Gas easily accumulates in the annular area between the mandrel and the mold sleeve, and existing venting structures cannot specifically cover this area, causing gas retention and internal defects. These defects can cause "local deflagration" or "uneven energy release" during combustion, and in severe cases, ignition failure.

[0004] The compression ratio of hollow gunpowder pellets during molding is typically as high as 40%-60% (i.e., the ratio of the initial filling height of the powder to the height of the molded pellet). However, the existing mold cavity structure is insufficient, resulting in uneven density distribution of the powder during the pressing process. The area of ​​the pellet near the upper mold core has a higher density due to direct pressure, while the area near the lower mold core has a lower density due to pressure transmission loss. The thin-walled area around the mandrel is prone to "density gradient difference" due to uneven stress. The causes are mainly twofold: First, the coaxiality error between the mold mandrel and the mold sleeve, and between the upper and lower mold cores, is relatively large (usually greater than 0.1mm). During pressing, the mandrel offset leads to uneven mold cavity gaps and inconsistent stress on the powder. Second, the existing upper and lower mold cores are cylindrical structures of equal diameter, which cannot optimize the pressure transmission path through structural design. Under high compression ratios, the pressure attenuates significantly along the axial direction, and there is no structure to guide the uniform flow of the powder, further exacerbating the density unevenness. When propellant grains with uneven density burn, the high-density areas burn slowly while the low-density areas burn quickly, resulting in a peak energy release fluctuation range exceeding 15%. This fails to meet the "precise flame control" requirement of ignition devices. Furthermore, the low-density areas have low mechanical strength, making them prone to cracking during transportation and assembly. Summary of the Invention The present invention aims to provide a hollow gunpowder column forming mold and forming method, so as to provide a gunpowder column with reliable forming quality.

[0005] A hollow gunpowder column forming mold includes a mandrel for forming the inner hole of the gunpowder column, a mold sleeve for forming the outer contour of the gunpowder column, upper and lower mold core assemblies for applying pressure, and a demolding assembly for demolding; the mandrel and the mold sleeve assembly are coaxially arranged to form a mold cavity for containing gunpowder powder; the mold sleeve is provided with an exhaust structure communicating with the mold cavity.

[0006] Working principle and beneficial effects of the present invention: The mandrel serves as the forming reference for the inner hole of the propellant grain, and its outer surface determines the shape and size of the inner hole. The inner surface of the mold sleeve serves as the forming reference for the outer contour of the propellant grain, and together with the mandrel, forms an annular mold cavity, providing a fixed forming space for the propellant powder. The upper and lower mold core assemblies apply axial pressure through a press, compacting the loose propellant powder in the mold cavity, making the powder particles tightly bound together to form a propellant grain with a fixed shape and density. The demolding assembly then separates and removes the propellant grain from the mold cavity after forming through a specific structural action.

[0007] During the pressing process, the air between the loose powder particles in the mold cavity is squeezed out. The air is then guided to the outside of the mold through the exhaust structure on the mold sleeve that is connected to the mold cavity, thus preventing air from being trapped inside the powder.

[0008] The optimized venting structure is a venting groove machined on the contact plane between the mold sleeve and the mandrel, with one end of the venting groove extending to the mold cavity and the other end extending to the edge of the mold sleeve; the lower mold core and the mold sleeve have a venting gap communicating with the venting groove.

[0009] During the pressing process, the air inside the mold cavity is subjected to pressure and flows from the end of the mold cavity to the edge of the mold sleeve along the venting groove from the venting gap, and is finally discharged outside the mold, thus preventing air from lingering in the contact gap between the mold cavity and the mandrel and mold sleeve.

[0010] Optimized, the venting groove is a Y-shaped groove. The Y-shaped structure can simultaneously cover multiple gas accumulation points in the mold cavity, improving venting efficiency.

[0011] The optimized mandrel is a stepped cylindrical structure with a forming column on one side and a top material groove on the cylindrical surface of the other side.

[0012] The optimized top material groove consists of two symmetrical semi-circular annular through grooves.

[0013] The optimized version includes an upper mold core and a lower mold core sleeved on the forming column.

[0014] The optimized demolding assembly includes a stripper frame with stepped holes at the top and bottom for placing the mold sleeve and rubber pad, respectively. The stripper frame is connected to an exhaust vent. It also includes an ejector rod that passes through the ejector slot to eject the lower mold core, the gunpowder column, and the upper mold core.

[0015] The upper stepped hole of the stripper frame matches the outer diameter of the mold sleeve, providing precise positioning for the inverted mold and ensuring that the mold axis and the ejector pin axis are coaxial during demolding. The rubber pad inside the lower stepped hole absorbs the impact load transmitted by the press during demolding, preventing hard contact that could damage the propellant. The vent is connected to the stripper frame, allowing the release of any residual gas in the mold cavity before demolding, reducing gas resistance during demolding. After the ejector pin passes through the ejector groove of the mandrel, it applies downward pressure under the drive of the press, indirectly pushing the lower mold core, propellant, and upper mold core downward as a whole through the mandrel, causing the propellant to detach from the mold sleeve and enter the stripper frame to complete demolding.

[0016] In the optimized configuration, the upper mold core, lower mold core, mold sleeve, vent, and stripper frame are all hollow cylindrical structures.

[0017] A method for forming a mold, comprising: Step 1: Place the mold cavity, consisting of the mandrel and the mold sleeve, onto the press; Step 2: Push the lower mold core into the bottom of the mold cavity; Step 3: Pour the mixed powder into the mold cavity, and level it after filling. Step 4: Place the powdered medicine from the upper mold core into the mold cavity; Step 5: Start the press to extrude the upper mold core, and form a gunpowder column between the upper and lower mold cores by mixing the powder. Step 6: Place the stripping frame with the rubber pad attached onto the press; Step 7: Invert the mold onto the stepped hole of the stripper frame; Step 8: Place the push rod into the semi-circular through groove of the mandrel; Step 9: Start the press to demold, and the ejector rod will push the gunpowder column into the ejector box.

[0018] The optimized components include: mandrel, upper mold core, and lower mold core, all made of Cr12MoV mold steel with a mandrel hardness of HRC50-55 and upper and lower mold core hardness of HRC60-62; mold sleeve made of 40Cr mold steel with a hardness of HRC57-62; stripper frame and venting nozzle made of aluminum rod; and ejector pin made of 45# carbon steel with a hardness of HRC40-45. Attached Figure Description

[0019] Figure 1 This is a front view of an embodiment of the molding die of the present invention; Figure 2 This is a front view of an embodiment of the demolding method of the present invention; Figure 3 This is a schematic diagram of the mandrel structure of the present invention; Figure 4 This is a schematic diagram of the mold structure of the present invention; Figure 5 This is a schematic diagram of the upper and lower mold core structures of the present invention; Figure 6 This is a schematic diagram of the unloading frame structure of the present invention; Figure 7 This is a schematic diagram of the exhaust nozzle structure of the present invention; Figure 8 This is a schematic diagram of the annular top rod structure of the present invention; Figure 9 This is a schematic diagram of the exhaust direction.

[0020] Figure reference numerals: 1. Mandrel; 2. Lower mold core; 3. Mold sleeve; 4. Upper mold core; 5. Stripper frame; 6. Rubber pad; 7. Vent; 8. Ejector rod. Detailed Implementation

[0021] The following detailed description illustrates the specific implementation method: A hollow gunpowder column forming mold includes: a mandrel 1, which is a stepped cylinder with one end of the cylinder being slender to form a forming column, and the other end of the cylinder having two symmetrical semi-circular annular through grooves on its flat surface, and countersunk screw holes and pin holes are machined therein. Lower mold core 2 is a hollow cylinder; Mold sleeve 3 is a hollow cylinder with a pin hole and a threaded hole machined on one end of its flat surface, and a Y-shaped groove machined for venting. Upper mold core 4 is a hollow cylinder; The stripper frame 5 is a hollow cylinder with stepped holes machined on both ends and threaded holes machined on the side. Rubber pad 6, rubber pad 6 is a flat cylinder; Exhaust nozzle 7 is a hollow cylinder with external threads machined on its outer surface. The push rod 8 has two slender semicircular rings that are symmetrical on the left and right sides on its disc.

[0022] A method for forming a mold, comprising: Step 1: Place the mold cavity, consisting of mandrel 1 and mold sleeve 3, onto the press; Step 2: Push the lower mold core 2 into the bottom of the mold cavity; Step 3: Pour the mixed powder into the mold cavity, and level it after filling. Step 4: Place the powdered medicine from the upper mold core 4 into the mold cavity; Step 5: Start the press to extrude the upper mold core 4, and form a gunpowder column between the upper mold core 4 and the lower mold core 2; Step 6: Place the stripping frame 5 with the rubber pad 6 attached onto the press; Step 7: Invert the mold onto the stepped hole of the stripper frame 5; Step 8: Place the push rod 8 into the semi-circular through groove of the mandrel 1; Step 9: Start the press to demold, and push the gunpowder column into the ejector box 5 with the ejector rod 8.

[0023] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A hollow gunpowder column forming mold, characterized in that, It includes a mandrel for forming the inner hole of the gunpowder column, a mold sleeve for forming the outer contour of the gunpowder column, upper and lower mold core assemblies for applying pressure, and a demolding assembly for demolding; the mandrel and the mold sleeve assembly are coaxially arranged to form a mold cavity for containing gunpowder powder; the mold sleeve is provided with a venting structure communicating with the mold cavity.

2. The hollow gunpowder column forming mold according to claim 1, characterized in that, The upper and lower mold core assembly includes an upper mold core and a lower mold core sleeved on the forming column.

3. The hollow gunpowder column forming mold according to claim 2, characterized in that, The venting structure is a venting groove machined on the contact plane between the mold sleeve and the mandrel. One end of the venting groove extends to the mold cavity, and the other end extends to the edge of the mold sleeve. There is a venting gap between the lower mold core and the mold sleeve that communicates with the venting groove.

4. The hollow gunpowder column forming mold according to claim 3, characterized in that, The exhaust groove is a Y-shaped groove.

5. The hollow gunpowder column forming mold according to claim 4, characterized in that, The mandrel has a stepped cylindrical structure with a forming column on one side and a top material groove on the cylindrical surface of the other side.

6. The hollow gunpowder column forming mold according to claim 5, characterized in that, The top material trough consists of two symmetrical semi-circular annular through-slots.

7. The hollow gunpowder column forming mold according to claim 6, characterized in that, The demolding assembly includes a stripper frame with stepped holes at the top and bottom for placing the mold sleeve and rubber pad, respectively. The stripper frame is connected to an exhaust vent. It also includes an ejector rod that passes through the ejector groove to eject the lower mold core, the gunpowder column, and the upper mold core.

8. The hollow gunpowder column forming mold according to claim 7, characterized in that, The upper mold core, lower mold core, mold sleeve, vent, and stripper frame are all hollow cylindrical structures.

9. The molding method of the mold according to any one of claims 1 to 8, characterized in that, include: Step 1: Place the mold cavity, consisting of the mandrel and the mold sleeve, onto the press; Step 2: Push the lower mold core into the bottom of the mold cavity; Step 3: Pour the mixed powder into the mold cavity, and level it after filling. Step 4: Place the powdered medicine from the upper mold core into the mold cavity; Step 5: Start the press to extrude the upper mold core, and form a gunpowder column between the upper and lower mold cores by mixing the powder. Step 6: Place the stripping frame with the rubber pad attached onto the press; Step 7: Invert the mold onto the stepped hole of the stripper frame; Step 8: Place the push rod into the semi-circular through groove of the mandrel; Step 9: Start the press to demold, and the ejector rod will push the gunpowder column into the ejector box.

10. The molding method of the mold according to claim 9, characterized in that, The mandrel, upper mold core, and lower mold core are made of Cr12MoV mold steel with a hardness of HRC50-55 and the upper and lower mold cores have a hardness of HRC60-62. The mold sleeve is made of 40Cr mold steel with a hardness of HRC57-62. The stripper frame and vent are made of aluminum rods. The ejector pin is made of 45# carbon steel with a hardness of HRC40-45.

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