Gas generator having a pyrotechnic propelling charge and method for producing the propelling charge
11433850 · 2022-09-06
Assignee
Inventors
Cpc classification
International classification
Abstract
A gas generator for use for a safety device in vehicles comprises a pyrotechnical propelling charge, wherein the propelling charge is formed from a first and at least a second master batch which are in a mixed state in a filling. Each master batch has a plurality of molded propellant bodies having defined geometry and having a relative quickness. The relative quickness RQ2 of the second master batch is less than the relative quickness RQ1 of the first master batch, wherein RQ2=RQ1.Math.fq and fq≤0.9. The invention further relates to a method for producing the propelling charge.
Claims
1. A gas generator comprising a pyrotechnical propelling charge, wherein the propelling charge is formed from a first and at least a second master batch which are in a mixed state in a filling, each master batch having a plurality of molded propellant bodies having defined geometry and having a relative quickness, wherein the relative quickness RQ.sub.2 of the second master batch is less than the relative quickness RQ.sub.1 of the first master batch, wherein RQ.sub.2=RQ.sub.1.Math.fq and fq≤0.9, and wherein the first and second master batches are mixed in predetermined amounts so that the propelling charge exhibits predetermined ballistic properties; wherein the molded propellant bodies of the first master batch and the second master batch have the same composition; wherein the molded propellant bodies of the first master batch have equal geometries; wherein the molded propellant bodies of the second master batch have equal geometries; and wherein the geometries of the molded propellant bodies of the first master batch are different than the geometries of the molded propellant bodies of the second master batch.
2. The gas generator according to claim 1, wherein the molded propellant bodies are present in the form of propellant pellets.
3. The gas generator according to claim 2, wherein the propellant pellets in the master batches have the same diameter but different height.
4. The gas generator according to claim 3, wherein the diameter is within a range of from 2 mm to 10 mm.
5. The gas generator according to claim 1, wherein the fq is within a range of from 0.4 to 0.9.
6. The gas generator according to claim 1, wherein the propelling charge is formed from more than two master batches, with RQ.sub.x denoting the relative quickness of one single master batch and being larger than the relative quickness RQ.sub.x+1 of the next master batch, wherein RQ.sub.x≥RQ.sub.x+1.Math.0.9.
7. The gas generator according to claim 6, wherein the propelling charge is formed from three master batches, with RQ.sub.1 denoting the relative quickness of the first master batch, RQ.sub.2 denoting the relative quickness of the second master batch and RQ.sub.3 denoting the relative quickness of the third master batch, wherein RQ.sub.1>RQ.sub.2>RQ.sub.3 and RQ.sub.1≥RQ.sub.2.Math.0.9 as well as RQ.sub.2≥RQ.sub.3.Math.0.9.
8. The gas generator according to claim 1, wherein the first master batch shows a time until reaching the maximum can pressure tpK.sub.max(1) measured in a can test and the second master batch shows a time until reaching the maximum can pressure tpK.sub.max(2) measured in equal test conditions in the can test, wherein tpK.sub.max(1).Math.ft=tpK.sub.max(2), wherein ft is within a range of from 1.35 to 3.2.
9. The gas generator according to claim 1, wherein the molded propellant bodies of the first and second master batches are produced by one of extrusion, dry pressing, and wet pressing.
10. The gas generator according to claim 1, wherein the molded propellant bodies of the first and second master batches are cylindrical, have the same diameter, and are cut to different lengths to produce their different geometries.
11. The gas generator according to claim 10, wherein the molded propellant bodies of the first and second master batches are produced by extrusion and include a through-hole.
12. The gas generator according to claim 1, wherein the respective relative quickness RQ is determined by testing a sample of 10 g of the respective propelling charge or master batch in a standard combustion chamber, wherein the standard combustion chamber is a closable vessel made from steel having a volume of 100 cm.sup.3, wherein the sample is ignited at room temperature within the standard combustion chamber by means of a pyrotechnical igniter and the increase in pressure during the propellant burn-off is detected by means of a piezo sensor having a scanning rate of 20 kHz so that it results in a pressure/time curve which is evaluated to determine the relative quickness RQ, and wherein the evaluation is based on the first derivation dp/dt of the pressure/time curve and the function values are established at the supporting points at 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8 p/p.sub.max of the first derivation and the mean value of the function values established at the supporting points corresponds to the respective relative quickness RQ.
13. A method for producing a pyrotechnical propelling charge for use in a gas generator comprising the following steps of: providing a first master batch consisting of a plurality of molded propellant bodies each having the same predefined geometry and a first relative quickness RQ.sub.1; providing a second master batch consisting of a plurality of molded propellant bodies each having the same predefined geometry and a second relative quickness RQ.sub.2, wherein the molded propellant bodies of the first master batch and the second master batch have the same composition, and wherein the relative quickness RQ.sub.2 of the second master batch is less than the relative quickness RQ.sub.1 of the first master batch, wherein RQ.sub.2=RQ.sub.1.Math.fq and fq≤0.9, the predefined geometry of the molded propellant bodies of the second master batch being different than the predefined geometry of the molded propellant bodies of the first master batch; and mixing a predetermined amount of the first master batch with a predetermined amount of the second master batch while forming the pyrotechnical propelling charge in the form of a filling in which the molded propellant bodies are present in a mixed state so that the propelling charge exhibits predetermined ballistic properties.
14. The method according to claim 13, wherein the molded propellant bodies are in a homogenously mixed state in the filling.
15. The method according to claim 13, wherein at least one further master batch consisting of pyrotechnical propellant comprising a plurality of molded propellant bodies having predefined geometry and a relative quickness RQ.sub.3 is provided, the geometry of the molded propellant bodies in the further master batch being different from the geometry of the molded propellant bodies in the first and second master batches and the relative quickness RQ.sub.3 of the further master batch being less than the relative quickness RQ.sub.2 of the second master batch, wherein RQ.sub.3=RQ.sub.2.Math.fq and fq≤0.9.
16. The method according to claim 13, wherein the ballistic property is selected from the group consisting of a relative quickness RQ of the pyrotechnical propelling charge, a maximum chamber pressure for the pyrotechnical propelling charge in a standard combustion chamber pBK.sub.max, a maximum can pressure for the pyrotechnical propelling charge in a can test pK.sub.max, a time until reaching the maximum chamber pressure for the pyrotechnical propelling charge in the standard combustion chamber tpBK.sub.max, a time until reaching the maximum can pressure for the pyrotechnical propelling charge in the can test tpK.sub.max, a maximum combustion chamber pressure of a gas generator pBKGG.sub.max utilizing the pyrotechnical propelling charge, a time until reaching the maximum combustion chamber pressure in the gas generator tpBKGG.sub.max utilizing the pyrotechnical propelling charge, and a burn-off rate and/or the burn-off duration of the pyrotechnical propelling charge.
17. The method according to claim 13, wherein the mixing of the master batches is carried out directly at a production line of the gas generator.
18. The method according to claim 13, wherein providing the first and second master batches comprises producing their respective molded propellant bodies by one of extrusion, dry pressing, and wet pressing.
19. The method according to claim 18, wherein producing the respective molded propellant bodies of the first and second master batches by extrusion comprises extruding the propellant bodies to be cylindrical in form with equal diameters, and wherein the propellant bodies of the first master batch are cut to a different length than the propellant bodies of the second master batch.
20. The method according to claim 19, wherein providing the first and second master batches comprises producing their respective molded propellant bodies by extrusion to include a through-hole.
21. The method according to claim 19, wherein the first and second master batches are included in the filling in a predetermined ratio, and wherein extruding the propellant bodies of the first and second master batches comprises cutting the respective propellant bodies to their respective lengths according to the predetermined ratio directly during the extrusion process.
22. The gas generator according to claim 13, wherein the respective relative quickness RQ is determined by testing a sample of 10 g of the respective propelling charge or master batch in a standard combustion chamber, wherein the standard combustion chamber is a closable vessel made from steel having a volume of 100 cm.sup.3, wherein the sample is ignited at room temperature within the standard combustion chamber by means of a pyrotechnical igniter and the increase in pressure during the propellant burn-off is detected by means of a piezo sensor having a scanning rate of 20 kHz so that it results in a pressure/time curve which is evaluated to determine the relative quickness RQ, and wherein the evaluation is based on the first derivation dp/dt of the pressure/time curve and the function values are established at the supporting points at 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8 p/p.sub.max of the first derivation and the mean value of the function values established at the supporting points corresponds to the respective relative quickness RQ.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Further features and advantages of the invention will be resulting from the following description and from the following figures which will be referred to and wherein:
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DESCRIPTION
(5) Production of the Master Batches
(6) A propellant powder made from 45% by weight of guanidine nitrate, 50% of basic copper nitrate and 5% of guar gum was ground and in dry state pressed into cylindrical propellant pellets having predefined dimensions. Instead of said 5% of guar gum, in general a 5% proportion of an additive may be used.
(7) The propellant pellets obtained in this way were provided as master batches in each of which only propellant pellets having defined geometry were present. In all master batches the diameter of the cylindrical propellant pellets was 6 mm. The height of the propellant pellets in the first master batch was 1.4 mm, in the second master batch it was 2.0 mm which also constitutes a reference batch, in the third master batch it was 2.4 mm and in the fourth master batch it was 3.0 mm.
(8) In the same way, another master batch was produced from propellant pellets having a diameter of 4.0 mm and a height of 1.3 mm.
(9) Mixing Tests and Ballistic Tests
(10) The master batches produced in this way were mixed in various proportions so that a propelling charge in which the propellant pellets of the respective master batches were present in a homogenous mixture in a filling was obtained.
(11) The ballistic properties of the master batches and of the propelling charges produced by mixing the master batches were examined by ballistic tests in the standard combustion chamber and in a standard gas generator. For the propelling charges and the master batches used for producing each of the propelling charges the same test conditions were employed, i.e. when examining the propelling charges (mixtures) and, resp., master batches the same test conditions were applied. Hence the master batches and the propelling charges were tested with the same charge, propellant composition, gas generator structure and volume of the respective test vessels. Thus, the variations of the ballistic parameters can be traced back solely to the geometry of the molded propellant bodies.
(12) A closed-off vessel having a defined volume (100 ccm) in which the propellant as such is burnt off is referred to as “standard combustion chamber”. Pressure/time curves which characterize the tested propellant in terms of ballistics are resulting from said test. The standard combustion chamber is a generally acknowledged means for examining the ballistic properties of pyrotechnical propellants and propelling charge powders. The relative change of the ballistic properties of the tested master batches and propelling charges are only dependent, in the case of an equal standard combustion chamber (volume), charge and equal propellant composition, on the geometry of the tested molded propellant bodies. Thus, the standard combustion chamber allows to compare the different propellant geometries without any further adaptation of the test rig used.
(13) In the so-called “can test”, a standard gas generator is loaded with a propelling charge and is activated in a closed test can having a defined volume (60 liters). Similar to the test in the standard combustion chamber, a pressure/time curve is obtained which may equally be used to characterize the respective propelling charge in terms of ballistics. Using the same gas generator with the same load and the same propellant composition, the relative variations among the propelling charges and master batches to be compared are only dependent on the geometry of the molded propellant bodies.
(14) The relative quickness was determined by testing the respective propelling charge or master batch in the standard combustion chamber. The standard combustion chamber used was a closable vessel made from steel having a volume of 100 cm.sup.3. 10 g of propellant were filled into the standard combustion chamber and the standard combustion chamber was closed. The propellant was ignited at room temperature by means of a pyrotechnical igniter. The increase in pressure during the propellant burn-off was detected by means of a piezo sensor having a scanning rate of 20 kHz. Said measurement results in a pressure/time curve which is evaluated to determine the relative quickness.
(15) To this end, the first derivation dp/dt of the pressure/time curve is formed and the function values are established at the supporting points at 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8 p/p.sub.max of the first derivation. The mean value of the function values established at the supporting points corresponds to the relative quickness RQ. The relative quickness RQ is a measure for the pressure variation per time [bar/ms] in the standard combustion chamber when the propellant is being burnt off.
(16) The following table 1 illustrates a comparison of the ballistic properties of the produced master batches from tests in the standard combustion chamber. Column “fq” indicates the RQ.sub.2 to RQ.sub.1 ratio with RQ.sub.1 denoting the relative quickness of the respective master batch having the smaller molded propellant bodies (1) and RQ.sub.2 denoting the relative quickness of the master batch having the molded propellant bodies (2) larger as compared to the first master batch. In column “ft” the corresponding ratio for the time until reaching the maximum pressure of the standard combustion chamber tpBK.sub.max(2) to tpBK.sub.max(1) is indicated.
(17) TABLE-US-00001 TABLE 1 Comparison of the master batches having different geometries in the standard combustion chamber Factors Master batch geometry ft = tpBK.sub.max(2)/ small (1) large (2) fq = RQ.sub.2/RQ.sub.1 tpBK.sub.max(1) 6 × 1.4 6 × 2.4 0.71 1.35 6 × 1.4 6 × 3.0 0.6 1.64 4 × 1.3 6 × 3.0 0.49 1.88
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(19) The results of the ballistic tests in the standard combustion chamber correlate with the results of the can test. Table 2 exemplifies a comparison of two master batches comprising propellant pellets of 6×1.4 mm and 6×2.4 mm with respect to the time until reaching the maximum can pressure tpK.sub.max; and, resp., the ratio of said respective times.
(20) TABLE-US-00002 TABLE 2 Comparison of master batches having different geometries in the can test Master batch geometry Factor small (1) large (2) tpK.sub.max(2)/tpK.sub.max(1) 6 × 1.4 6 × 2.4 1.79
(21) In the following table 3, the ballistic parameters obtained from the can test and by the examination in the standard combustion chamber for the first, second and third master batches are indicated. Moreover, the ballistic parameters of propelling charges obtained from mixtures of the first and third master batches are additionally indicated. For carrying out the can test, a common gas generator was loaded with 72 g of propellant and was activated in a closed test can (60 l/10 bar) at room temperature. The test in the standard combustion chamber was carried out as described before in connection with establishing the relative quickness. In the table pK.sub.max denotes the maximum can pressure, tpK.sub.max denotes the time until the maximum can pressure is reached and RQ denotes the pressure variation per time in [bar/ms] in the standard combustion chamber.
(22) TABLE-US-00003 TABLE 3 Ballistic properties of master batches and propelling charges from mixtures of master batches Propelling charges Ballistic parameters Master batches [mm] pK.sub.max [bar] tpK.sub.max [ms] RQ [bar/ms] 6 × 1.4 3.9 54.2 15.9 6 × 2.0 3.6 81.3 12.3 6 ×2.4 3.5 97.1 10.9 Mixing ratio 6 × 1.4 [%] 6 × 2.4 [%] pK.sub.max [bar] tpK.sub.max [ms] RQ [bar/ms] 50 50 3.6 64.4 13.1 40 60 3.5 70.1 13.2 30 70 3.5 81.2 12.2 20 80 3.4 88.4 11.7 10 90 3.4 95.0 11.2
(23) It is evident from the table that the ballistic properties of the second master batch, viz. the reference batch, including propellant pellets of 6×2.0 mm can be reconstructed by a 30/70 mixture of the first and third master batches comprising propellant pellets of 6×1.4 mm and 6×2.4 mm. In this case, the proportion of the smaller propellant pellets of the first master batch in the propelling charge produced by mixing the master batches is below the proportion to be expected from the pellet height. Hence, in proportion more propellant pellets of the third master batch having larger dimensions are required to achieve the ballistic goal.
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