Abstract
A matrix for shaping a valve preform has a circular through opening and a reduced conical section. The reduced conical section tapers from an outer diameter to a reduced cone inner diameter, the outer diameter being greater than or equal to the initial outer diameter of the valve preform, and the matrix inner diameter being smaller than the initial outer diameter.
Claims
1-12. (canceled)
13. A tapering machine for shaping a valve preform, comprising a matrix for shaping a valve preform, the matrix having a circular through opening and a reduced conical section, wherein the reduced conical section tapers from an outer diameter of the opening of the matrix to a reduced cone inner diameter of the matrix, and wherein the outer diameter of the opening of the matrix is greater than or equal to an initial outer diameter of the valve preform, and the matrix reduced cone inner diameter is smaller than the initial outer diameter, and further including a pressing device an a pressing device controller than are configured for pressing the valve preform with a stem section thereof into the matrix with an oscillating motion.
14. The tapering machine for shaping a valve preform according to claim 13, wherein the reduced conical section of the matrix comprises a first reduced conical section, and wherein the matrix also includes a second reduced conical section, and wherein a transition section is situated between the first and the second reduced conical sections.
15. The tapering machine for shaping a valve preform according to claim 14, wherein the transition section between the first and the second reduced conical sections is cylindrical.
16. The tapering machine for shaping a valve preform according to claim 14, wherein the transition section expands between the first and the second reduced conical sections.
17. The tapering machine for shaping a valve preform according to claim 14, wherein the matrix includes a cylindrical calibration section behind the reduced conical section and the second reduced conical section.
18. The tapering machine for shaping a valve preform according to claim 17, the matrix also includes a calibration mandrel which on a free end includes a calibration bulb, wherein the calibration mandrel can be pulled through the matrix from an area of the reduced conical section or of the second reduced conical section to one endo f a calibration section.
19. The tapering machine according to claim 18, further comprising a calibration mandrel tensioning device that is configured, after a valve preform is pressed with a hollow stem into the matrix, to pull the calibration mandrel from ahead section of the valve preform, through a stem section of the valve preform, and out of a stem end.
20. A method for shaping a hollow valve preform a valve preform using a tapering machine having a matrix with a circular through opening and a reduced conical that tapers from an outer diameter of the opening to a reduced cone inner, and wherein the outer diameter is greater than or equal to an initial outer diameter of the valve preform, and the matrix reduced cone inner diameter is smaller than the initial outer diameter of the valve preform, and further including a pressing device and a pressing device controller that are configured for pressing the valve preform with a stem section thereof into the matrix with an oscillating motion, the method comprising the steps of: Providing the valve preform with a head section and the hollow stem section having initial outer diameter, Pressing the hollow stem section into the matrix with the initial outer diameter that is tapered to the reduced cone inner diameter, Controlling the pressing device of the tapering machine with the pressing device controller in such a way that the valve preform with the stem section is pressed into the matrix with an oscillating force and/or an oscillating path.
21. The method for shaping a hollow valve preform according to claim 20, wherein the reduced conical section is a first reduced conical section that tapers a stem section of the valve preform to a first reduced conical section inner diameter, and a second reduced conical section of the matrix further tapers the stem section of the valve preform, which is already tapered to the first reduced conical section inner diameter, to an inner diameter of the second reduced conical section inner diameter.
22. The method for shaping a hollow valve preform according to claim 21, wherein the transition section expands between the first and the second reduced conical sections, and wherein the stem section that is tapered to the first reduced conical section inner diameter once again increases in terms of a partial elastic deformation to a larger outer diameter than the first inner diameter.
23. The method for shaping a hollow valve preform according to claim 21, wherein the matrix includes a cylindrical calibration section behind the reduced conical section and the second reduced conical section, wherein an end outer diameter of the tapered or twice-tapered stem section is calibrated by a cylindrical portion of the matrix.
24. The method for shaping a hollow valve preform according to claim 23, wherein the matrix also includes a calibration mandrel which on a free end includes a calibration bulb, wherein during pressing in of the valve preform in the at least one tapering step of the matrix, the calibration bulb is inserted in front of an area of the reduced conical section or the second reduced conical section, and wherein after the tapering, the calibration mandrel with the calibration bulb is pulled through the reduced conical section or the second reduced conical section and through the calibration section and out of the stem end.
25. The method of claim 13 wherein the oscillating motion has a corresponding oscillating force.
26. The method of claim 13 wherein the oscillating motion has a corresponding oscillating path.
27. The method of claim 26, wherein the oscillating path comprises a forward movement step followed by a correspondingly smaller reverse movement step.
Description
[0025] The present invention is explained below with reference to schematic illustrations of exemplary embodiments.
[0026] FIG. 1 shows a one-stage matrix for tapering a stem section of a valve preform.
[0027] FIGS. 2A through 2G illustrate individual steps of a method for shaping a valve preform to form a valve blank.
[0028] FIG. 2H illustrates an unsuccessful tapering attempt.
[0029] FIGS. 3A through 3G illustrate possible substeps of the method in FIGS. 2C through 2E.
[0030] FIG. 4 shows a one-stage matrix having an additional calibration section.
[0031] FIGS. 5A through 5D illustrate a shaping operation using the matrix in FIG. 4.
[0032] FIG. 6 shows a special form of the one-stage matrix from FIG. 4, which is also provided with a calibration mandrel.
[0033] FIGS. 7A through 7F illustrate a shaping operation using the matrix in FIG. 4, in which the cavity is calibrated in a separate step.
[0034] FIGS. 8A through 8C show two two-stage matrices and a one-stage matrix.
[0035] FIGS. 9A through 9E illustrate a shaping operation using the matrix in FIG. 8A, in which the cavity is calibrated in a separate step.
[0036] FIGS. 10A and 10B show two two-stage matrices that are additionally provided with a calibration section.
[0037] FIGS. 11A through 11E illustrate a shaping operation using the matrix in FIG. 10A, in which the cavity is calibrated in a separate step.
[0038] In the following discussion, identical or similar reference symbols are used for identical or similar elements and components in the description and in the figures.
[0039] FIG. 1 shows a one-stage matrix 2 for tapering a stem section of a valve preform. The matrix 2 includes a through opening 4 having a circular cross section. The through opening 4 includes a reduced conical section 6 in which the through opening 4 tapers from an inlet diameter E of the matrix 2 to a reduced cone inner diameter R of the matrix 2. The reduced cone inner diameter R here also determines the matrix inner diameter.
[0040] A mating cone or a straight section may be situated behind the reduced cone inner diameter. An insertion structure such as a run-in cone or a rounded section may be present in front of the reduced cone to facilitate entry of a stem section of a valve preform into the matrix.
[0041] In the present design, the matrix essentially forms a draw plate as known from the shaping process of wire drawing. In contrast to wire drawing, however, the matrix is intended for a stem section of a valve preform to be pressed into the matrix from the outside or from below. Thus, a completely different load situation is present. In addition, a mating cone, which is mandatory in a draw plate, may be dispensed with in the matrix. Therefore, in one design the matrix also has no mating cone, and instead, the tapered or reduced cone merges directly into a cylindrical section as illustrated.
[0042] FIGS. 2A through 2G illustrate individual steps of a method for shaping a valve preform 40 to form a valve blank. The valve preform 40 includes a disk section 42, also referred to as a head section, and a stem section 44, the material of which subsequently forms a valve stem. A cavity 46 that extends from one end of the stem section 44 in the direction of the disk section 42 is situated in the stem section. In one aspect of the invention, the cavity in the area of the disk section 42 has a radius that is larger than that of a stem of the subsequent valve. In this way a cavity may be produced in a valve relatively easily, the cavity having a larger diameter in the head of the valve than could be achieved by machining. The stem section 44 of the valve preform 40 has an initial outer diameter A that is smaller than an inlet diameter E of the matrix 2.
[0043] In FIG. 2B, the stem section 44 of the valve preform 40 has been pressed approximately halfway into the matrix 2 in FIG. 1. In the process, the initial outer diameter A has been reduced to a tapered outer diameter A.sub.v. The tapering has reduced both the outer diameter and the inner diameter of the stem section, whereas the length of the stem section has been increased by the shaping.
[0044] In FIG. 2C, the matrix 2 has been removed after being moved toward the disk section 42 (i.e., the valve preform 40 has been pressed into the matrix 2 up to the disk section 42). The once-tapered stem section 44 of the valve preform 40 may now be further tapered with an additional matrix having a smaller inner diameter. It is possible to subject the valve preform 40 to stress relief annealing to facilitate a subsequent tapering step.
[0045] FIG. 2D corresponds to FIG. 2B, only using a smaller matrix and the valve preform in FIG. 2C, which has already been deformed once.
[0046] FIG. 2E corresponds to FIG. 2C; however, the valve preform has been shaped in two steps.
[0047] FIG. 2F corresponds to FIGS. 2B and 2D, only using an even smaller matrix, and the valve preform in FIG. 2E, which has already been deformed twice, is further tapered.
[0048] FIG. 2G shows a valve preform that has been shaped a sufficient number of times that it may be regarded as a valve blank. FIG. 2E corresponds to FIG. 2D; however, the valve preform has been shaped in two steps. The cavity of the valve blank may now be partially filled with a coolant such as sodium and closed. It is likewise possible to machine an outer surface of the valve blank to achieve desired surface qualities and tolerances.
[0049] FIG. 2H schematically shows the main problem during a tapering step, namely, the risk of the stem section buckling or bulging in or out during tapering. Since the tapering subjects the material to pressure, the pressure force at which failure of the stem section occurs is limited. For this reason, the stem section of the valve preform must also be tapered in multiple steps. Depending on the selected material, significantly more than three passes may be necessary to shape a valve preform into a valve blank.
[0050] FIGS. 3A through 3G illustrate possible substeps of the method in FIGS. 2C through 2E. Instead of a single shaping operation, in the present case shaping is carried out intermittently or in sections. In FIG. 3A, the stem section with approximately one-fourth of its length is pressed into the matrix with great force in a working stroke H.sub.A, as indicated by the long, thick arrows. The small path prevents the stem section from buckling.
[0051] In FIG. 3B, the stem section has been pulled slightly out of the matrix in a reverse stroke H.sub.R. At this point a lubricant may be introduced between the matrix or the reduced cone and the stem section, thus allowing a further reduction in the force required for the tapering.
[0052] In FIG. 3C, the stem section with approximately an additional one-fourth of its length is pressed further into the matrix with great force as in FIG. 3A, as indicated by the long, thick arrows. The small path prevents the stem section from buckling.
[0053] In FIG. 3D, the stem section has been pulled slightly out of the matrix. At this point a lubricant may once again be introduced between the matrix or the reduced cone and the stem section.
[0054] In FIG. 3E the stem section is now pressed with great force into the matrix until reaching the disk section. Since the untapered tapered stem section is shorter and has a more favorable position [sic; length] to diameter ratio, the last portion may be shaped with a working stroke H.sub.A without the risk of the undeformed stem section buckling. It is thus possible to carry out working strokes H.sub.A and reverse strokes H.sub.R here in alternation. It is likewise provided to increase the larger [sic; magnitude] or the length of the working strokes H.sub.A in each case. It is preferred to start with small working strokes H.sub.A and increase their length linearly. It is further preferred to start with small working strokes H.sub.A and progressively increase their length.
[0055] In FIG. 3G, the stem section has been pulled completely out of the matrix in a long reverse stroke H.sub.R. The other shaping steps as explained for FIGS. 2A through 2G may likewise be carried out with an oscillating path or alternating working strokes and reverse strokes. The pressing in with an oscillating path may also be used as explained below.
[0056] FIG. 4 represents a matrix that essentially corresponds to the one illustrated in FIG. 1. In addition, the matrix is provided with a calibration section 18 in which the tapered stem section is guided and directed. The tapered stem section cannot yield laterally in the matrix, as the result of which a straight stem may be achieved. A straight stem may be more easily shaped in a subsequent matrix, since it has a lesser tendency to break out to the side. The greater precision is attained here by a greater pressing-in force, which corresponds to a lower degree of tapering.
[0057] However, in the method in FIGS. 3A through 3G, the friction component in the calibration section 18 may be kept low by use of lubricant.
[0058] FIGS. 5A through 5D correspond to FIGS. 2C through 2E. Here as well, the oscillating pressing-in method from FIGS. 3A through 3G may be utilized to achieve a higher degree of tapering.
[0059] FIG. 6 shows a special form of the one-stage matrix from on FIG. 4, which is additionally provided with a calibration mandrel 20. The calibration mandrel at a free end includes a calibration bulb 22 that includes a calibration cone 24 and a mating cone 26 on one side.
[0060] The calibration mandrel is moved essentially independently of the matrix itself. During pressing in, the calibration mandrel 20 is not moved with respect to a disk section 42 of the valve preform 40, and is not used to maintain a defined gap between the calibration bulb 22 and the reduced section during pressing in.
[0061] In FIG. 7A, the calibration mandrel 20 together with the calibration bulb 22 is lowered down to the bottom of the cavity of the valve preform 40. An outer diameter of the calibration bulb 22 is smaller than an inner diameter of the cavity 46. The calibration bulb corresponds to exactly one turned-up draw plate as known from wire drawing.
[0062] In FIGS. 7B and 7C, the stem section 44 of the valve preform 40 is pressed into the matrix 2, and the calibration mandrel is moved together with the valve preform 40. The calibration bulb 22 remains at the base of the cavity 46 during the pressing in.
[0063] During the pressing into the matrix, the inner diameter of the stem section is reduced to the tapered inner diameter. The tapered inner diameter is smaller than an outer diameter of the calibration bulb 22.
[0064] In FIG. 7D, the calibration mandrel 20 is pulled through the stem section and out of the cavity 46. The calibration bulb 22 pushes material of the stem section in front of it, thus further increasing the length of the stem section. At the same time, the outer diameter of the stem section and its wall thickness are made uniform.
[0065] Lastly, in FIG. 7E the tapered, calibrated stem section of the valve preform is pulled out of the matrix 2. The tapered, calibrated stem section of the valve preform has the same outer diameter A.sub.v as an uncalibrated stem section. The tapered, calibrated stem section of the valve preform has a larger calibrated inner diameter A.sub.vIK than the uncalibrated stem section from FIG. 5D.
[0066] FIGS. 8A through 8C show two two-stage matrices and a one-stage matrix.
[0067] The matrix in FIG. 8C corresponds to the one-stage matrix shown in FIG. 1, with a single reduced cone, and is used here for illustration only. The matrix 2 includes a reduced conical section 6 that tapers from an inlet diameter E to a reduced cone inner diameter R. The reduced cone inner diameter R here also determines the matrix inner diameter. A simple mating cone is situated behind the reduced cone.
[0068] The matrix in FIG. 8A represents a two-stage matrix having a first reduced cone 8 and a second reduced cone 16. A cylindrical transition section 12 is situated between the first reduced cone 8 and the second reduced cone 16. The first reduced cone 8 has a first inlet diameter E.sub.1. The first reduced cone 8 tapers to a first reduced cone inner diameter R.sub.1. The second reduced cone 16 has a second inlet diameter E.sub.2, which in this case is equal to the first reduced cone inner diameter R.sub.1. The second reduced cone 16 tapers from the second inlet diameter E.sub.2 to the second reduced cone inner diameter R.sub.2.
[0069] The aim is for the difference between E.sub.1 and R.sub.2 to be greater than the difference between E and R of the matrix from FIG. 8C. This is possible due to the fact that a lower load on the material may be achieved when two tapering stages are carried out in succession.
[0070] The matrix in FIG. 8B represents a two-stage matrix having a first reduced cone 8 and a second reduced cone 16. A diverging transition section 14 is situated between the first reduced cone 8 and the second reduced cone 16. The first reduced cone 8 has a first inlet diameter E.sub.1. The first reduced cone 8 tapers to a first reduced cone inner diameter R.sub.1. The second reduced cone 16 has a second inlet diameter E.sub.2 that is larger than the first reduced cone inner diameter R.sub.1. The second reduced cone 16 tapers from the second inlet diameter E.sub.2 to the second reduced cone inner diameter R.sub.2. The matrix here has the shape of two draw plates situated in direct succession. This shape is not suitable for wire drawing, since the tensile load cannot be absorbed by a thinner wire.
[0071] FIGS. 9A through 9E illustrate a shaping operation using the matrix in FIG. 8A, in which the stem section is tapered in two stages with each pressing-in operation.
[0072] FIGS. 10A and 10B show the two-stage matrices in FIGS. 8A and 8B, which are additionally provided with a calibration section 18.
[0073] FIGS. 11A through 11 E illustrate a shaping operation using the matrix in FIG. 10A, in which the cavity is calibrated in a separate step. The method corresponds to the one illustrated in FIGS. 7A through 7G. However, the calibration concerns only the portion of the tapered stem section that has been tapered from the second reduced cone.
LIST OF REFERENCE SYMBOLS
[0074] 2 matrix [0075] 4 through opening [0076] 6 reduced conical section [0077] 8 first reduced conical section [0078] 10 transition section [0079] 12 transition section (cylindrical) [0080] 14 transition section (expanding) [0081] 16 second reduced conical section [0082] 18 calibration section (cylindrical) [0083] 20 calibration mandrel [0084] 22 calibration bulb [0085] 24 calibration cone [0086] 26 mating cone [0087] 40 valve preform [0088] 42 disk section/head section [0089] 44 stem section [0090] 46 cavity [0091] A initial outer diameter of the stem section of the valve preform [0092] E inlet diameter of the matrix [0093] R reduced cone inner diameter of the matrix, also matrix inner diameter [0094] A.sub.v tapered outer diameter of the valve preform [0095] A.sub.v1 tapered inner diameter of the valve preform [0096] A.sub.vIK calibrated tapered inner diameter of the valve preform [0097] E.sub.1 first inlet diameter or inlet diameter of the first reduced conical section [0098] R.sub.1 first reduced cone inner diameter or inner diameter of the first reduced conical section [0099] A.sub.v1 first tapered outer diameter of the valve preform [0100] A.sub.vI1 first tapered inner diameter of the valve preform [0101] E.sub.2 second inlet diameter or inlet diameter of the second reduced conical section [0102] R.sub.2 second reduced cone inner diameter or inner diameter of the second reduced conical section, also smallest matrix inner diameter [0103] A.sub.v2 second tapered outer diameter [0104] A.sub.vI2 second tapered inner diameter of the valve preform [0105] A.sub.vIK2 second calibrated tapered inner diameter of the valve preform [0106] H.sub.A working stroke [0107] H.sub.R reverse stroke
