Method for the production of an internal stop in a tubular component

Abstract

An inner diameter of a first end of a tubular component, positioned in relation to a first die, is reduced through relative movement between the tubular component and the first die such as to produce a first conical area between first and second ends of the tubular component. The first conical area is then formed through relative movement of a second die to create in a longitudinal section of the first conical area an outer circumferential embossment and an inner bead having an inner diameter smaller than the inner diameter of the first end. The first end is widened through insertion of an inner tool, while the tubular component is supported on an outside in a mold cavity of an outer tool. An inner contour with an internal stop is formed as an outer surface of the first end of the tubular component rests flatly in the mold cavity.

Claims

1. A method, comprising the steps of: positioning a tubular component of steel in relation to a first die having an inner diameter which is smaller than an outer diameter of the tubular component; reducing an inner diameter of a first end of the tubular component by a relative movement between the tubular component and the first die in an axial direction of the tubular component such as to produce a first conical area between the first end of reduced inner diameter and a second end of the tubular component; forming the first conical area by a relative movement of a second die in the axial direction of the tubular component in a direction of the second end of the tubular component, so as to create in a longitudinal section of the first conical area a circumferential embossment on an outside and a bead on an inside, with the bead having an inner diameter which is smaller than the reduced inner diameter of the first end; widening the first end of the tubular component by inserting an inner tool axially into the first end of the tubular component, while the tubular component is supported on an outside in a mold cavity of an outer tool; and forming an inner contour with an internal stop as an outer surface of the first end of the tubular component rests flatly in the mold cavity.

2. The method of claim 1, further comprising producing during formation of the inner contour a circumferential stepped shoulder which is spaced from an end face of the first end of the tubular component and includes a first step defined by an inner diameter and an adjacent second step defined by an inner diameter which is greater than the inner diameter of the first step, with the internal stop being formed in a transition zone between the first step and the second step.

3. The method of claim 2, wherein the inner diameter of the second step is smaller than the inner diameter of the first end of the tubular component which first end is situated anteriorly of the second step.

4. The method of claim 2, wherein during formation of the inner contour in an area of the second step a wall thickness is produced which is greater than a wall thickness in a non-deformed length section of the tubular component.

5. The method of claim 2, wherein the second step is produced with an axial length which is greater than an axial length of the first step.

6. The method of claim 1, wherein the tubular component is produced as a housing of a gas generator module, with the internal stop providing a positional orientation of an inner component of the gas generator module.

7. The method of claim 6, wherein the method is carried out on a combustion chamber side of the housing to be produced.

8. The method of claim 1, wherein the inner tool includes a first inner tool to widen the first end and a second inner tool to subsequently form the inner contour in an area of the bead.

9. The method of claim 1, wherein the internal stop is rounded or chamfered.

10. The method of claim 1, wherein the tubular component is made of a high-strength steel alloy with a strength of Rm>780 MPa.

11. The method of claim 1, wherein the tubular component is made of a high-strength steel alloy with a strength of Rm>1050 MPa.

12. The method of claim 1, wherein at least one of the forming steps is carried out as a cold forming process.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

(2) FIG. 1 is a simplified illustration of a longitudinal section through a formed area of a tubular component as housing of a gas generator module;

(3) FIGS. 2.1-2.4 illustrate a chronological sequence of four production steps in a first forming tool;

(4) FIGS. 3.1-3.4 illustrate a chronological sequence of four production steps in a second forming tool;

(5) FIGS. 4.1-4.4 illustrate a chronological sequence of four production steps with a third forming tool;

(6) FIGS. 5.1-5.4 illustrate a chronological sequence of four production steps with a fourth forming tool;

(7) FIG. 6 is a detailed cutaway view of a formed first end of the tubular component; and

(8) FIG. 7 is an enlarged detailed view of the area encircled in FIG. 6 and marked VII.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(9) Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments may be illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

(10) Turning now to the drawing, and in particular to FIG. 1, there is shown by way of example a longitudinal section of a portion of a tubular housing 2 of a gas generator module. The tubular housing 2 is made from an originally cylindrical tubular component 1, with the further production steps involving an axial cold forming process being explained with reference to FIGS. 2.1-5.4. FIG. 1 shows the tubular component 1 with a first end 3 and a second end 5. The tubular component 1 is formed with an embossment 8 that is designed to run circumferentially radially on the outside and to have different diameter zones (inner diameters D6 and D7) at first and second steps 23, 24 of a stepped shoulder 21, with an internal stop 22 being formed between the steps 23, 24.

(11) The tubular component 1 is advantageously made of high-strength steel with a strength Rm of >780 MPa. Currently preferred is the use of a tubular component 1 made of high-strength steel with a strength Rm of >1050 MPa. According to the illustration of FIG. 2.1 the tubular component 1 is positioned on a first die 4. As indicated in FIG. 2.2, the first die 4 has an inner diameter D2 which is smaller than an outer diameter D1 of the tubular component 1. In a manner not shown in detail, the second end 5 of the tubular component is axially supported and/or held. The first die 4 is axially displaced in a direction of arrow P1. The original inner diameter D3 of the tubular component 1 is being reduced to a smaller inner diameter D4.

(12) FIG. 2.3 shows the lower end position of the first die 4. FIG. 2.4 shows how the first die 4 is moved back into the starting position in a direction of arrow P2. The inner contour of the first die 4 with stepped inner diameter D2 has been transferred to the tubular component 1. A first conical area 6 was formed, which is situated between the non-deformed second end 5 and the deformed first end 3. As a result of the forming process, the first end 3 was slightly stretched. The transitions between the conical area 6 and the first and second ends 3 and 5 are rounded.

(13) Resetting takes place in a second forming stage (FIGS. 3A-3.4). This means that the cylindrical part of the first end 3, which has already been formed, is not formed again, but rather the conical area 6. For this purpose, provision is made for a second die 7 which also has a gradation in order to form anew the first conical area 6. FIG. 3.2 shows how the second the 7 is displaced in a direction of arrow P1 in an axial direction. FIG. 3.3 shows the second the 7 in a lower end position. The first conical area 6 was deformed, with a circumferential embossment 8 and an inwardly protruding bead 25 now being produced in the original length area of the first conical area 6. The wall area at the level of the embossment 8 has shifted radially inwards. An inner diameter D5 of the bead 25 is smaller than the inner diameter D4 of the already formed cylindrical first end 3.

(14) The embossment 8, which is designed to run circumferentially radially on the outside, is followed in axial direction by a second widening conical area 9 which is formed by the second die 7 and represents the transition to the second end 5 of the tubular component 1, which second end 5 remains non-deformed. The transitions are smooth. The second conical area 9 is steeper than the first conical area 6 as a result of the corresponding shape of the second die 7, as can be seen from a comparison of FIGS. 2.4 and 3.4. FIGS. 2.4 and 3.4 each show the first and second dies 4 and 7 during the upward movement in the direction of arrow P2 and at the same time the tubular component 1 as a result of the respective formation stage.

(15) FIGS. 4.1 to 4.4 show the next production step. The tubular component 1 with the contour according to FIG. 3.4 is inserted in an outer tool 10 with a mold cavity 11. The mold cavity 11 is contoured, i.e. it is not exclusively cylindrical, and determines the later outer shape of the tubular component 1.

(16) An inner tool 12 is inserted in the direction of arrow P1 from the first end 3 into the tubular component 1, so that the tubular component 1 is widened. The first inner tool 12 has a frustoconical tip 13, which is followed by a cylindrical shaft 14. Corresponding to the contour of the first inner tool 12, a cylindrical contour is accordingly produced in the upper region of the first end 3 of the tubular component 1 and a conical contour is produced in the region in which the tip 13 comes into contact with the tubular component 1, approximately up to the level of the embossment 8 or of the inwardly directed bead 25.

(17) FIG. 4.3 shows a lower end position of the first inner tool 12. FIG. 4.4 again shows the upward movement (arrow P2) of the first inner tool 12 in the outer tool 10 and the contour of the tubular component 1 after completion of this production step.

(18) FIG. 4.4 also shows that the cylindrical outer surface 15 of the tubular component 1 rests upon the mold cavity 11 in the region of the first end 3. In the more strongly contoured areas adjacent to the embossment 8, the tubular component 1 does not yet rest upon the mold cavity 11 of the outer tool 10.

(19) The final calibration is explained with reference to FIGS. 5.1-5.4. The tubular component 1 with the contour according to FIG. 4.4 is shown in FIG. 5.1. A second inner tool 16 has a head 17 with several gradations (FIG. 5.2). A slimmer shaft 18 adjoins the head 17 (FIG. 5.3). The second inner tool 16 has three stepped diameter zones as active surfaces for the forming process. The area of the head 17 with the greatest diameter comes initially into contact with the first end 3 of the tubular component 1 and calibrates the inner diameter of the first end 3 over the majority of its length.

(20) The smaller diameter zones of the head 17 are situated anteriorly in axial direction and in the forming direction. Corresponding to the contour of the head 17, there are also two further diameter zones of smaller diameter in the mold cavity 11. In the area of the embossment 8, the mold cavity 11 has a projection 19 which engages in the embossment 8.

(21) FIG. 5.3 shows a lower end position of the second inner tool 16. In the area of the projection 19, the embossment 8 in the wall of the tubular component 1 is pressed outwards against the mold cavity 11. The material is pressed in particular against the projection 19 of the mold cavity 11. The area with the smallest inner diameter is thereby formed, so that an inner contour 20 with a circumferential stepped shoulder 21 is created, as shown in FIG. 5.4.

(22) In FIG. 5.4, the second inner tool 16 is in the phase of the upward movement in the direction of arrow P2. The formed tubular component 1 can now be removed from the outer tool 10.

(23) FIG. 6 shows an enlarged illustration of the finished stepped shoulder 21, which is spaced from an end face 26 (FIG. 5.4) of the first end 3 of the tubular component 1. The stepped shoulder 21 has an internal stop 22 which is arranged at a transition zone between the first step 23 of smaller inner diameter D6 and the second step 24 of greater inner diameter D7 along the transition zone. The greater second step 24 is situated anteriorly of the smaller first step 23 in accordance with the contour of the second inner tool 16.

(24) FIGS. 6 and 7 show further details in the area of the stepped shoulder 21. The greater step 24 has a greater axial length L1 than the rounded stop 22, which has a length L2. In addition, the length L1 of the greater step 24 is also greater than the length L3 of the step 23 of smaller diameter. The length L3 of the smaller step 23 is greater than the length L2 of the stop.

(25) FIGS. 6 and 7 further show that the end-side length region of the first end 3, which end-side length region is disposed anteriorly of the formed stepped shoulder 21 and which is also essentially cylindrical, has a greater inner diameter D8 than the inner diameter D7 of the greater second step 24. At the same time, the wall thickness W1 is substantially constant over the entire forming area. There is only a slight thickening in the area of the greater second step 24, which in this exemplary embodiment is approximately 1/10 mm. The outer diameter D1 is preferably in a range of 20 mm-50 mm with wall thicknesses W1 of 1.5 mm-3 mm and with a thickening of the wall thickness W1 of 5%-20%.

(26) FIGS. 6 and 7 further show radii R. The radii R have different sizes. All transitions are smooth, except between the internal stop 22 and the smaller first step 23. Diameter information is only given in the essentially cylindrical areas. The outer diameter D9 in the formed area with the greatest diameter is smaller than the outer diameter D10 of the greater second step 24. In addition, the ratio between the outer diameters D1, D9 at the non-deformed second end 5 and in the deformed area can be governed by the following equation: D9=0.9−1.0×D1.

(27) In the length region of the internal stop 22, the embossment 8 has a rounded transition radially on the outside toward the second step 24 with greater outer diameter D10. The depth T1 of the embossment 8 in relation to the outer diameter D10 of the greater second step 24 is in a range from 0.3 mm-1 mm. The rounded embossment 8 merges into the non-deformed area of the second end 5 via a further rounded transition with the radius R.

(28) While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.