JP2809032B2 - Propellant grain molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming propellant grains, and more particularly to a method for forming an internal combustion type propellant grain of a solid rocket motor.

[0002]

2. Description of the Related Art As shown in FIG. 4, an internal combustion type propellant grain (solid propellant) 1 having a hollow portion 2 having a radial cross section as represented by a star shape is formed. Molding is performed using a core mold 5 as shown in FIG.
4 is a motor chamber of the solid rocket motor, and 4 is a nozzle.

That is, as shown in FIGS. 5 and 6, a blade portion 6 corresponding to the shape of the hollow portion 2 is provided in a motor chamber 3 having an inner peripheral surface subjected to a combustion suppressing process by sticking a restrictor or the like. The core mold 5 is set, and the slurry propellant 7 is poured into the space formed by the motor chamber 3 and the core mold 5 to cure the solid propellant 7. 8 will be used to pull out the core mold 5. Incidentally, as a technique similar to this technique, there is one disclosed in JP-A-63-277846.

In this case, considering the ease of pulling out the core mold 5, for example, 1/500
While a taper of about a degree is used to provide a so-called draft, the outer peripheral surface of the core mold 5 is coated with Teflon having a thickness of about 30 to 50 microns to improve the releasability.

[0005]

However, in the conventional molding method as described above, even if the core mold 5 has been subjected to a mold release treatment, the load required for pulling out the core mold 5 is extremely large. Large, for example 400m in diameter
Even in the case of a rocket motor having a length of 2,500 mm and a length of 2,500 mm, the load required for pulling out the core mold 5 reaches several tons, which is an extremely troublesome work requiring carefulness as the core mold drawing operation.

Here, it is understood that the load required for pulling out the core mold 5 becomes large as follows. Since the propellant 7 injected into the motor chamber 3 is shrunk when hardened, a stress relief mechanism is provided to prevent shrinkage cracking at the motor end face. Therefore, it is considered that a compressive stress acts on the core mold 5 in the axial direction at the end of the motor chamber 3 and a stress in the opposite direction occurs at the center. Therefore, it is presumed that a negative pressure is generated at the center of the boundary surface between the core 5 and the solid propellant 1, and this negative pressure appears as a resistance when the core 5 is pulled out. Is done.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a molding method capable of easily extracting a core after molding a solid propellant.

[0008]

According to the present invention, a core mold is placed in a molding container, and a slurry-like propellant is poured into a space formed by the molding container and the core mold and cured. In a propellant grain forming method in which a hollow inner combustion type propellant grain is formed by extracting a core from a solid propellant in the forming container, the number of outer peripheral surfaces of the core is The method is characterized in that a cloth-like body is previously adhered along the drawing direction over the entire length in the longitudinal direction, and molding is performed in a state where a non-breathable surface film is adhered on the cloth-like body. And

[0009]

According to this method, the cloth-like material sandwiched between the surface of the core mold and the surface film functions as an air passage, and the core mold and the propellant mix with each other as the propellant cures and shrinks. Even if a negative pressure is generated at the center of the boundary, the negative pressure is released to the atmosphere through an air passage provided by the cloth.
Therefore, the resistance at the time of removing the core die can be reduced.

[0010]

1 to 3 show an embodiment of the present invention.
Portions common to the conventional example shown in FIGS. 5 and 6 are denoted by the same reference numerals.

As shown in FIGS. 2 and 3, on the outer peripheral surface of the core die 5 having a radial cross section, a cloth-like body is previously formed along the core die pulling-out direction over the entire length in several longitudinal directions. While a bleeder cloth 9 having a predetermined width is adhered, a surface film 10 such as a Teflon film having excellent releasability is adhered on the bleeder cloth 9 as shown in FIG.

When the bleeder cloth 9 and the surface film 10 are attached, they are fixed to the core mold 5 using a minimum amount of tape 11, as shown in FIG. The bleeder cloth 9 is obtained by coating a glass cloth with Teflon in order to improve the releasability. Also,
It is important that the above-mentioned surface film 10 does not have air permeability in order to prevent the propellant 7 from entering the bleeder cloth 9 and clogging. Moreover, it is preferable that the bleeder cloth 9 is made of a plain weave in order to make the thickness as thin as possible and to prevent the bleeder cloth 9 from being pressed by the propellant 7 and biting into the propellant 7.

The core mold 5 to which the bleeder cloth 9 and the surface film 10 are attached in this manner is separated from the core mold 5 shown in FIG.
As shown in FIG. 3 (B), a slurry-like space is formed in a space formed by the motor chamber 3 and the core mold 5 as shown in FIG. The propellant 7 is poured and cured to form the solid propellant (propellant grain) 1.

At this time, even if a negative pressure is generated at the center of the boundary between the core 5 and the propellant 7 as the curing of the propellant 7 proceeds as in the prior art, the negative pressure is maintained at the core type. The bleeder cloth 9 sandwiched between the film 5 and the surface film 10 is opened to the atmosphere as an air passage.

When the propellant 7 in the motor chamber 3 has hardened, the core 5 is pulled out of the formed solid propellant 1 using a hydraulic jack or the like. In this case, since the negative pressure does not act on the boundary between the core 5 and the solid propellant 1 as described above, the core 5 can be relatively smoothly extracted from the solid propellant 1.

In the above-described embodiment, an example of the direct charging system in which the slurry-like propellant 7 is directly poured into the motor chamber 3 to form the solid propellant 7 has been described. The present invention can be similarly applied to the molding of a solid propellant in the case of employing a block bonding method (block molding method) in which a restrictor or the like is wound and then charged into a motor chamber.

[0017]

As described above, according to the present invention, when a slurry-like propellant is poured into a space formed by a molding container and a core mold to form a hollow inner combustion type propellant grain, At several places on the outer peripheral surface of the core mold, a cloth-like body is pasted in advance along the core mold pull-out direction over the entire length in the longitudinal direction, and a non-breathable surface film is pasted on the cloth-like body. Due to the contact, the cloth-like body sandwiched between the core mold and the surface film functions as an air passage, so even if a negative pressure is generated at the boundary between the core mold and the propellant, the above-mentioned condition is obtained. It will be released to the atmosphere through the cloth.

Therefore, unlike the prior art, the above-mentioned negative pressure does not become a resistance when extracting the core mold, and the core mold can be smoothly extracted from the solid propellant. This has the effect of facilitating the sampling operation and improving its workability.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of the present invention, wherein (A) is an explanatory view of a state in which a core type is set in a motor chamber, (B)
FIG. 2 is an explanatory view of a state in which propellant is poured into the motor chamber, and FIG. 2C is a sectional view of a main part of a core.

FIG. 2 is a perspective view of the core type shown in FIG.

FIG. 3 is an enlarged view of a main part of FIG. 2;

FIG. 4 is a view showing an example of an internal combustion type propellant grain;
(A) is a sectional view thereof, and (B) is a sectional view taken along the line bb of FIG.

FIG. 5 is an explanatory view showing a conventional solid propellant grain forming method.

FIG. 6 is a perspective view of the core shown in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Solid propellant (propellant grain) 2 ... Hollow part 3 ... Motor chamber (molding container) 5 ... Core type 7 ... Slurry propellant 9 ... Bleeder cloth (cloth-like body) 10 ... Surface film

Claims (1)

(57) [Claims] 1. A core mold is placed in a molding container, a slurry propellant is poured into a space formed by the molding container and the core mold, and the slurry is hardened. In a propellant grain forming method in which a hollow inner combustion type propellant grain is formed by extracting a core mold from a propellant, at several places on an outer peripheral surface of the core mold, a total length in a longitudinal direction thereof is provided. A method of forming a propellant grain, characterized in that a cloth-like body is previously adhered along the above-mentioned drawing direction, and molding is performed while a non-breathable surface film is adhered on the cloth-like body. .