US3754060A - Process for production of propellant charges comprising compressing geometrically shaped powders together - Google Patents

Abstract

A PROCESS FOR PRODUCING SHAPED POWDER ARTICLES FOR PROPELLENT CHARGES BY PRESSING POROUS POWDER GRAINS HAVING EXTERNAL GEOMETRIC SHAPES EXHIBITING EDGES, SPIKES OR THE LIKE WHICH PERMIT THE GRAINS TO INTERLOCK WITH EACH OTHER. PREFERABLY THE GRAINS HAVE T, X, Y, OR V-SHAPES, ALSO DSCLOSED ARE SHAPED POWDER ARTICLES PRODUCED BY THIS PROCESS.

Description

United States Patent m 3,754,060 PROCESS FOR PRODUCTION OF PROPELLANT CHARGES COMPRISING COMPRESSING GEO- METRICALLY SHAPED POWDERS TOGETHER Heinz Gawlick, Furth, Bavaria, and Giinther Marondel, Erlaugen, Germany, assignors to Dynamit Nobel Aktiengesellschaft, Germany No Drawing. Filed Aug. 2, 1971, Ser. No. 168,370 Claims priority, application Germany, Aug. 1, 1970, P 20 38 288.1 Int. Cl. C0611 21/02 US. Cl. 264-3 C 11 Claims ABSTRACT OF THE DISCLOSURE A process for producing shaped powder articles for propellant charges by pressing porous powder grains having external geometric shapes exhibiting edges, spikes or the like which permit the grains to interlock with each other. Preferably the grains have T, X, Y, or V-shapes. Also disclosed are shaped powder articles produced by this process.

The present invention deals with shaped powder articles and a process for making the same for use as propellant charges, wherein no solvent or binder is utilized.

It is conventional to manufacture formed powder articles for propellant charges by mixing the grains of the propellant powder with a suitable solvent or a binder, and then pressing the mixture into the desired shape. During the pressing step, an inherently cohesive body of powder is then produced. This process, however, exhibits disadvantages. When solvents are used, the latter can be driven out of the pressed articles only with difiiculty. Moreover, the necessary drying procedure inherently changes the geometric configuration so that the desired exact dimensions of the pressed articles cannot be attained with certainty. The use of adhesives undesirably inhibits the deflagration of the powder body, whereby a non-uniform burning generally occurs leaving non-combusted residues.

A process for the production of shaped powder articles for propellant charges by compressing powder grains has now been found which is characterized in that porous powder grains are used in the pressing step which exhibit a bulky, geometric configuration interlocking on the outer ends (exterior).

It was surprisingly discovered that, when such powder grains are pressed together, shaped bodiesare obtained which exhibit the same mechanical strength as shaped powder articles pressed with the aid of solvents or binders, but which do not have the above-mentioned disadvantages.

Powder grains exhibiting the above-disclosed bulky configurations are already known. They can consist of singleor multiple-base, conventional propellant powders. However, preferably, they consist of pure nitrocellulose powder because of its variable porosity. It is also possible to use, as other components of the propellant powder grains, different explosives or mixtures of these substances which are slow-burning or react under deflagration without tending to detonate, such as, for example, polyvinyl nitrate, nitroguanidine, or penthrite. The powder grains to be pressed should, in this connection possess, if possible, the maximum density prior to the pressing step.

The geometric form of the powder grains must be fashioned so that they exhibit on the surface several pro- 3,754,060 Patented Aug. 21, 1973 jecting arms or spikes (tips, points, etc.), so that a projecting arm or a spike of one powder grain engages in the interstices between two arms or spikes of another grain. Grain configurations meeting these conditions most advantageously are the T-shape, X-shape, Y-shape, or V-shape.

The powder grains must be porous prior to pressing. The porosity is extensively determined by the desired burning velocity and the geometry of the powder grain.

The pressing of the powder grains to form caseless propellant charges is conducted in a conventional manner. Due to the angular configuration of the individual grains, the pressure employed in the processing step need not be excessively high to produce a mechanically strong shaped article. Even at a pressure of 400-500 kp./cm. firm shaped articles are obtained. Advantageously pressures of between 1600 and 5000 kp./cm. are used for the pressing process.

Due to the fact that the pressure during the pressing step is not excessively high, the porosity of the individual powder grain is partially preserved in the finshed shaped powder article.

An additional advantage is that the shaped powder article can again be separated into the powder grains from which is was produced, during the ignition process. Thereby, the burning characteristic of the original powder grain is obtained with uniform burning.

EXAMPLE By means of a hydraulic press, tablets 2.5-30.0 mm. in thickness were pressed from a propellant powder in a pressing die at a pressure of 4000 kp./cm. The propellant powder exhibited the following properties: Individual powder grains were porous exhibiting an angular shape, similar to a V- or Y-configuration. The powder was about 98% nitrocellulose with an N-content of 13.1%.

The strength of the thus-pressed tablets was determined by using a testing arrangement consisting of two planarparallel plates having an almost frictionless parallel guidance.

The pressed article is placed, on edge, between the plates, and one of the plates is burdened by weights disposed thereon until the pressed article is broken. The value of the weights employed is indicative of the strength of the pressed article.

The pressed bodies produced according to the abovernentioned exampleexhibited a strength ranging between 4.0 and 11.0 kp., depending on the configuration and size of the grain.

It is understood that the embodiments disclosed herein are susceptible to numerous changes and modifications, as will be apparent to a person skilled in the art. Accordingly, the present invention is not limited to the details shown and described herein but intended to cover any such changes and modifications within the scope of the invention.

We claim:

1. A process for the production of shaped powder articles for propellant charges comprising pressing together propellant powder grains fashioned to have external geometric angular shapes exhibiting projecting arms or spikes so that the arms or spikes of said angular-shaped grains interlock with each other.

2. The process of claim 1 wherein said powder grains are porous.

3. The process of claim 2 wherein said powder grains comprise dry propellant powders.

4. The process of claim 3 wherein said powder grains comprise nitrocellulose.

5. The process of claim 3 wherein said dry propellant powders comprise at least one substance which is slowburning or reacts under deflagration without tending to detonate.

6. The process of claim 5 wherein said at least one substance is polyvinyl nitrate, nitroguanidine, penthrite, 10

10. The process of claim 9 wherein said pressure is between about 1600 and 5000 kp./cm.

11. The process of claim 2 wherein said powder grains exhibit at least one configuration selected from the group of T, X, Y, or V-shapes.

References Cited UNITED STATES PATENTS 7/1962 Grubaugh 264-3 C 6/1968 Nix et al. 1492 X STEPHEN J. LECHERT, 111., Primary Eaminer US. Cl. X.R.