FI61864C - SAETT ATT FRAMSTAELLA FAERDIGFORMAT KRUT MED LAOG VATTENHALT OCH EN SAMMANSATT YTTRE UTFORMNING EXEMPELVIS I FORM AV EN STAENG - Google Patents

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ΉΒΓφ LJ '} UTLÄGGNINGSSKRIFT Dl 004 c (4S) Patent granted II 10 1932

Patent ^ nicdJe-lat (51) Kv.ik? /int.ci? e 06 B 21/00 £ U O M I - FINLAND (21) P »t« nttlh * k «mut - Patantantöknlng 2786/7 ^ (22) Htkamlspllv! - Anteknlngidag 2 ^ .09-7 ^ (23) AlkupUvI - Glltlghatsdag 2 ^ .09 · 7 ^ + (41) Become Public— Bllvlt © fientilg 27. 03.75

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Patent · OCh reglsterttyrelsen 'Ainekin utligd och utl. * Krlftin pgblicirad 30.06.82 (32) (33) (31) Pyyd «** y etuoikeus — Begird prlorltet 26.09.73

Sweden-Sweden (SE) 7313076-7 (71) AB Bofors, S-690 20 Bofors, Sweden-Sweden (SE) (72) Bror Torsten Alexis Persson, Karlskoga, Mats Jvirgen Martin Olsson, Karlskoga, Sweden-Sweden (SE) (7M Berggren Oy Ab (5 ^) A method of making a preformed powder having a low water content and a uniform appearance, for example a rod shape - Sät att framställa färdigformat Krut med läg vattenhalt och en sammansatt yttre utfomming a preformed powder having a low water content and a uniform appearance, for example a rod shape, from the aqueous powder mass by compressing and at the same time removing from the screw press the excess liquid formed by water and / or solvent which continuously separates the powder mass when compressed.

In this context, it has previously been proposed to achieve a final external design of the powder in somewhat different ways depending on the type of powder, namely either a thermoplastic design, or by means of design volatile solvents. Gunpowder can be divided into species on several different grounds; according to its main components, into monobasic, dibasic and tribasic powders, according to the auxiliary gelling agents, into solvent-containing and solvent-free powders or into different species according to the geometric shape of the finished powder.

The monobasic process contains mainly cellulose nitrate, while the dibasic process also contains glycine 2,61864 rinitrate as the second main component. The tri-base powder consists mainly of stvlulosan nitrate, glycerin nitrate and guanidine nitrate.

Ether, spirits or acetone are usually used in the preparation of solvent-containing powders for the co-gelling agent. Ether and spirits are commonly used in the preparation of monobasic powder and acetone in the preparation of two- and three-base powder. The solvent is added to the cellulose nitrate to facilitate gelation so that it can be passed through at lower temperatures and at a lower degree of modification. As a result, the production of solvent-containing powders is considered less hazardous than the production of solvent-free powders. However, solvent-containing powders have the disadvantage of having difficulty drying them. However, if the wall thickness is thicker than a few mm, the ether or spirits content can be reduced by drying and dissolving to such low values that they do not affect the ballistic stability. In practice, the acetone content is more difficult to reduce to the same extent, and solvent residues of about 0.5 to 1% are common in finished powder. This knows that acetone-containing powder is clearly inferior to acetone-free powder compared to ballistic stability. Moreover, the production of acetone-containing powder is somewhat more extensive, both momentarily and in time.

In the preparation of the monobasic extract, water is displaced from the moistened cellulose nitrate by ethanol. In this case, for example, presses or centrifuges are used, and cellulose nitrate containing about 30% ethanol is obtained. As such, cellulose nitrate is transferred to kneading equipment, and during kneading, stabilizers and other additives dissolved in ether are added. After kneading, the further nitrated portion of the cellulose nitrate will be more or less unchanged within the jelly formed by the less nitrated cellulose nitrate. The powder is then extruded into its final shape. The powder can then be pre-dried in large coils, whereby most of the ether evaporates. The powder can then be cut while still soft due to its spirits content, and then screened, dried, etc.

Two- and three-base powders are made in part by a different technique. Cellulose nitrate is slurried in water. Glycerol nitrate and other additives are then added, which are absorbed by the cellulose nitrate without significantly altering its shape as a result, but retaining its structure consisting mainly of discrete fibers. The powder pulp thus prepared is centrifuged to a water content of about 30%.

For example, in the preparation of acetone-free two- and three-base powders, additives which could not be mixed in the wet mixing step, e.g. soot, lubricant and guanidine nitrate, are first added to the kneading equipment. This is followed by shaping between the heated rolls in several steps, whereby the powder mass gels under pressure and heat and changes from a fibrous, soft powder to a uniform, homogeneous mat. In this case, drying takes place at the same time, first by squeezing out water from the powder mass and then by evaporating from the hot powder mat.

In the next stage of manufacture, the gunpowder acquires its final, geometric shape. In the case of pipe powder, this is done by pressing it through several ring nozzles into rods, which are then cut into pieces; for leaf and strip powder by rolling into a sheet which is then cut. The preformed powder is usually conditioned in a hot air stream to a specified moisture content.

This type of manufacturing has many drawbacks. Intermittent work requires a lot of labor. For safety reasons, small quantities are processed at the same time in several rolling mills, which also causes difficulties in obtaining a uniform product. Large-scale production accumulates large amounts of dry gunpowder, which poses a fire hazard. Fires in rolling mills are common, and even more so, gunpowder ignites when pressed.

Moreover, it is very difficult to achieve acceptable working conditions in the production of gunpowder according to conventional technology. Although glycerol nitrate is relatively volatile, it evaporates to such an extent that the permissible hygienic limits for the concentration of glycerol nitrate in the air are exceeded unless the work areas are extremely well ventilated. Moreover, when preparing powder according to the old method, it is unavoidable that the personnel come into direct contact of the glove with warm powder, in which case glycerol nitrate penetrates the skin unless protective gloves are used which interfere with work.

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The primary object of the method according to the invention is to solve the above-mentioned problems by feeding the pulp into the press as an aqueous suspension or as a granulate mixed with water. When compressing the pulp in the press, the excess liquid separates from the pulp as water and / or solvent. According to the invention, this excess liquid and the free water supplied to the press with the powder are continuously sucked out through screened outlets located close to the inlet end of the press. Only when the press is provided with outlets for the active removal of excess liquid and free water can the pulp be fed to the screw press together with a larger amount of water than the pulp can absorb and still make the capacity of the press satisfactory.

This new approach is suitable for continuous operation, while safety in the workplace can be improved, on the one hand, by handling small quantities of powder in relation to production capacity and, on the other hand, by simply remote control of the process in question. Safety is also significantly improved by keeping all the gunpowder and tufted mass under water during processing, which reduces the risk of fire in the manufacturing facilities. The method according to the invention also causes the need for labor to be reduced, while the manufacturing process becomes more pleasant for the labor by avoiding direct contact with the hot powder. Finally, this new method also makes it possible to compress more complex powder shapes.

It is already known, inter alia, from French Patent Publication No. 1,596,363 to use screw presses in connection with powder bar pressing, but the procedures used in the screw presses mentioned therein have not been found to have the great advantages of feeding water to the screw presses in question in Tuutima.

A device of the type disclosed in Swedish patent 202 079, consisting of a screw press with overflow channels for discharging excess liquid as a self-flowing liquid, hardly survives pulps containing up to as much water as the powder itself can absorb, and if the excess water is greater than 5 61 864 are the outlets of the press are completely inadequate.

Another way to prepare a rod-like powder from a very high liquid starting material is disclosed in U.S. Patent 3,223,756, starting from a solution of the powder mass in a water-soluble alcohol and injecting this solution into a water bath where it gels and the solvent is removed by washing.

Another similar method, according to which the powder mass is formed in an extruder in a jelly-like state, is disclosed in Finnish Patent 46,371.

According to one embodiment of the invention, the powder, which requires a lot of mechanical processing in order to obtain the correct degree of gelation, can be screw-pressed in at least two different screw presses with the drying carried out in between. The powder is then cut into pieces after leaving the first press and dried, after which it is re-mixed with water and fed as a new aqueous suspension or granules in water to a second press where a new dewatering and associated final shaping is performed.

A proposed embodiment having the features of the invention will now be described with reference to the accompanying drawing, in which Figure 1 is a vertical view of the basic structure of the equipment used in accordance with the invention, Figure 2 is a vertical view of the equipment complement of Figure 1 and Figure 3 is a partially sectioned elevational view , which shows the suitable screw clamp in more detail.

In Fig. 1, reference numeral 1 denotes a screw press which is attached at one end to a stand 2, which in turn is attached to a base 3. To this base are also attached screw press actuators 4. The upper part of the base 2 supports a feed container 5 provided with a , operated by actuators 6 on top of the tank 5.

61818 The container 5 is connected at its bottom by a supply pipe 7 to at least one feed opening 5 of a screw press.

From the tank 8, which is only partially drawn, the pulp is injected as an aqueous suspension or granules mixed with water into the feed tank 5 down the line 9 through the nozzle 10. Thus, said aqueous suspension or mixture of granulate and water is fed to the screw press immediately through the pipe 7 and the feed openings of the press.

From the point of view of good operation of the press, it is advantageous if the grain size in the aqueous suspension is somewhat larger than in a conventional powder mass. This is accomplished by heating the suspension together with a solvent for cellulose nitrate that is only sparingly soluble in water, e.g., methyl ethyl ketone or ethyl acetate. The fibers then clump into granules which are suitably allowed to grow to a size of about 1 mm. The solvent concentration and heating time required for this depend on the composition of the powder and must be searched experimentally in each case. Depending on the type of powder to be produced, the solvent in the powder mass is completely or partially evaporated before the aqueous suspension is discharged into the feed tank 5 · The aqueous suspension does not need to be centrifuged but can be transferred to the feed tank immediately after cooling without spinning. In the case where the above-mentioned solvent is completely removed, this can be carried out in 2-H per hour due to the porous structure of the granules, reaching a solvent content of less than 0.1%. The product thus becomes equivalent to the conventionally prepared solvent-free powders.

In order to increase the downfeed speed in the screw press, this is suitably provided with a suction nozzle 11, not shown in more detail, which includes a strainer, for discharging the main part out of the water. The suction effect is provided by a pump 12, through which the sucked-out water is returned to the supply tank along the line 13.

The free end of the screw press is provided with an outlet nozzle from which the treated gunpowder exits in the form of rods 14. According to Fig. 1, the rods pass through a special guide member 15 to the cutting machine 61864 7. Transport from the discharge nozzle to the cutting machine takes place in water in a suitable temperature in this application example, in troughs not shown in more detail. A water separator 17 »is arranged at the inlet of the cutting machine, the water separated by which is returned via a hopper 18 to a suitable point in the process cycle. In the cutting machine, the rod-shaped powder is cut into pieces of the desired length, after which the powder can be dried in a stream of hot air.

In some cases, where high requirements are placed on the porosity of the powder, for example in the case of rocket powder, more than one, e.g. two, presses can be used. In this case, two identical screw presses according to the previous one connected in series can be used. The first screw press is then fed in the same way as above, said powder sludge, and is connected, as shown in Fig. 2, immediately from its discharge nozzle to a cutting machine 19 with rotating blades, which cuts the powder from the first screw press into small pieces. can be obtained, for example, up to line 21.

The contents of the container 20 can then be transferred in the process chain to the supply container 5 of the second screw press connected after the first screw press. This transfer takes place down the line 22. The rod-shaped powder obtained from the second screw press can then be fed to the cutting machine 16.

Generally speaking, the advantages of feeding the powder in water are achieved in that, for example, in the case of glycerol nitrate powder, which must be cut and then hand-held, it becomes cooled, and in the case of cellulose nitrate powder, which must be cut immediately at the die, it improves safety.

A more detailed view of a screw press suitable for use with the method described above is shown in Figure 3. .

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The screw and its sleeve can be kept at a suitable temperature by means of circulating water. The cooling ducts for this purpose and their inlet lines 27 and outlet lines 28 are also shown in Figure 3 ·

Pressure and temperature are measured at several points along the screw press with pressure and thermometers that can be connected to a process control system. The gauges are marked with the number 29 in Figure 3 ·

The screw press is equipped with circumferential nozzles and has a special outlet in the middle for a different, more aqueous powder. The water in question has accumulated on the screw and exited its tip as a noros in the middle of the powder stream. The second-grade powder is re-granulated and returned to the process further.

The relevant components, which are not explained in more detail above, may be known per se.

The invention is not limited to the embodiment exemplified above, but may be modified within the scope of the appended claims.

Claims (2)

9 1. Sätt att framställa färdigformat Krut med läg vattenhalt oeh en mossansatt yttre utformning, exempelvis i forma av en sträng, av en wattenhaltig krutmassa genom compressing av krutmassan en en screw, under the same conditions as the scraper press at the same time, or, in the case of cross-cutting, compression of the conveyor belt with water density, as well as non-coarse-grained compression of the screw conveyor and in the form of a water suspension, alternatively genom silförsedda ut-vég i närheten av Pressens inloppsände. 1. A method of making a preformed powder having a low water content and a uniform appearance, for example a rod shape, from an aqueous powder mass by compressing the powder mass in a screw press while removing from the screw press the excess water and / or solvent continuously known from the powder mass; that the pulp is fed to the press as an aqueous suspension or granulate mixed with water and that the free water supplied and the liquid separated from the powder when compressed are continuously sucked out through screened outlets located near the inlet end of the press. A method according to claim 1, wherein the pulp is screw-pressed in at least two different screw presses with drying, characterized in that after the powder has passed through the first press and possibly broken into smaller pieces, it is dried and immediately followed by mixing with water and a new aqueous suspension or as granules mixed with water, it is fed to a second press where a new dewatering and associated pre-shaping is performed. 2. Sät enligt patentkravet 1, varvid krutmassan screw screw and minst there was a screw screw press with a second-hand screw, the transverse pressure of which is set to pass the genome of the press and, if necessary, the capacitor up to the current, the form of a water suspension or a granule is added to the water during and after the press, which means for the manufacture of water and the use of the same formulation.