Method and casting mould arrangement having a sensor device for detecting the presence of a metal melt

Abstract

The invention relates to a casting mould arrangement and a method casting mould arrangement for detecting the presence of a metal melt in the casting mould arrangement. A sensor device (S1, S2) can selectively measure the presence of the metal melt in that a dielectric coating (M1) is arranged at least on a part of the inner side of the casting mould wall (2), wherein the sensor device (S1, S2) has a draining coaxial line (4) with an open end, wherein the coaxial line (4) has an inner conductor (5) arranged in a sensor receptacle (3) of the casting mould wall (5) and a dielectric (7) extending between the inner conductor (5) and an outer conductor (6), wherein the open end of the coaxial line (4) adjoins the dielectric coating (M1), wherein, by means of the electronics unit, a transmission signal (18) with a frequency f is applied to the coaxial line (4), wherein the signal (19) returning from the coaxial line (4) is evaluated by means of the electronics unit (16).

Description

[0001] "METHOD AND CASTING MOLD ARRANGEMENT WITH A SENSOR DEVICE FOR DETECTING THE PRESENCE OF MOLTEN METAL" The invention relates to a casting mold arrangement with the features of the preamble of patent claim 1 and a method with the features of the preamble of patent claim 8. At least one sensor device is used to detect the presence of molten metal in the casting mold arrangement, wherein the casting mold arrangement has a casting mold wall and at least one sensor device arranged in the casting mold wall, wherein a transmission signal is sent to the sensor device and a reception signal is passed from the sensor direction to an electronic unit, wherein the presence or absence of the molten metal is detected by means of a change in the reception signal. The sensor devices are also referred to as sensors below. A casting mold arrangement with several sensors in the form of measuring sections is known from DE102018116952A1.The measuring sections are used to monitor the flow of molten metal during casting. The measuring sections are manufactured in advance and arranged in corresponding receptacles in the casting mold. The measuring sections have a transmitting coil and a receiving coil with one wire turn and are arranged at a distance from each other within an insulating material, for example, in compressed sand. The measuring sections are essentially ring-shaped. When the molten metal is poured into the casting mold, the melt passes through the measuring sections one after the other. As it passes through the respective measuring section, the melt is detected. The halves of the casting mold form an electrical waveguide of the measuring section. Thus, the transmitting coil and the receiving coil are each arranged within a waveguide. An electrical signal is applied to the transmitting coil whose carrier frequency is below the lowest cutoff frequency of the waveguide.This generates a highly concentrated, locally focused electromagnetic field. The presence or absence of melt in the area of ​​the measuring section influences the received signal. When melt enters the area of ​​the measuring section, the presence of the melt within the measuring section can be detected by the change in the received signal. The coils are severed when the mold is opened. This arrangement is suitable for permanent molds and sand molds for manual casting. In practice, the interior of the mold can be sprayed with an anti-stick compound so that the solidified workpiece can be removed from the die-casting tool. The two-part construction of the die-casting tool, the use of the electrically insulating anti-stick compound with coils surrounding the sprue, and the automation of the casting process complicate the design of the measuring arrangement.Furthermore, the presence of molten metal cannot be measured at a specific point, but only in the section of the measuring sections. The use of measuring sections in casting molds with highly curved surfaces is complex. The publication by Siqi Fan, Katie Staebell, Devendra Misra entitled "Static Analysis of an Open-Ended Coaxial Line Terminated by Layered Media" (IEEE Trans. on Instrumentation and Measurement, pp. 435-437, Vol. 39, No. 2, April 1990) investigates the electrical properties, namely the capacitance, of an open coaxial conductor. The open end of the coaxial conductor is adjacent to a first layer of a dielectric and a second layer is adjacent to the side of the first layer facing away from the coaxial conductor. The dependence of the capacitance of the arrangement on different dielectric materials for the first layer is investigated: water, dioxane, and methanol.The second layer should be formed either by an air layer or a metal layer. This publication is referred to below as paper [1]. From Werner Bächtold's book "Lineare Elemente der Höchstfrequenztechnik" (Linear Elements of High-Frequency Technology), 2nd edition, 1998, vdf, the inductance per unit length L is used as the characteristic parameters of a coaxial conductor. ^ and the capacity C ^and the wave impedance ZW are specified. This publication is referred to below as book [2]. The invention is therefore based on the object of designing and developing the sensor device in such a way that the sensor device can measure the presence of the molten metal at specific points, can be used along the inner surface even on surfaces with strong 3D curves, and has a design as simple and robust as possible in the gate and in the mold due to the adverse environment. Furthermore, it is advantageous if the necessary electronics do not require expensive measuring devices, such as a network analyzer or spectrum analyzer. This object on which the invention is based is now achieved by a casting mold arrangement with the features of patent claim 1. A dielectric coating is arranged on at least part of the inside of the casting mold wall.According to the invention, the sensor device comprises an open-circuit coaxial cable with an open end. The coaxial cable has an inner conductor arranged in a sensor receptacle of the mold wall and a dielectric extending between the inner conductor and an outer conductor. The open end of the coaxial cable borders the dielectric coating. The open end is also separated from the molten metal by the dielectric layer. The end of the coaxial cable borders this dielectric layer made of a first medium, so-called medium 1. Medium 1 is an initially liquid "anti-stick" solution that is injected into the mold before the die-casting process, solidifies, and is intended to prevent the solidified workpiece from sticking in the mold. The open end is particularly flush with the inner surface of the mold wall.The open end thus forms a very small part of the mold, and the cable cross-section of the coaxial cable can be selected to be very small. The invention has several advantages. The sensor device can be designed to be small and can therefore measure the presence of the molten metal at specific points. Due to its small extension along the inner surface, the sensor device can also be used on surfaces with strong 3D curves. The sensor device has a simple and robust design. Furthermore, no expensive measuring devices such as a network analyzer or a spectrum analyzer are necessary. The casting mold wall can also be referred to as a mold and is typically made of metal, thus forming a metal mold. The sensor holder is preferably formed by a bore. The sensor holder extends from the outside of the casting mold to the inside. The metal mold is provided with a bore with a specific diameter Ø^.In an alternative embodiment, the diameter of the sensor receptacle and also the diameter of the sensor device arranged therein widen from the outside to the inside. The sensor receptacle can be conical. This has the advantage that, during a die-casting process, the high pressures are supported on the inner walls of the sensor receptacle, thus improving the fastening of the sensor device. In one embodiment, the outer conductor is designed as a separate component that is arranged, in particular fastened, in the sensor receptacle. The coaxial line is formed by a coaxial cable that is attached to the sensor receptacle. This separate component is referred to as the metal shield. The outer diameter of the metal shield is dimensioned such that the metal shield can be easily pushed into the sensor receptacle. The outer diameter is smaller than or equal to the diameter of the sensor receptacle.There are different ways in which the metal shield can be connected to the casting mold. In particular, a component with an internal thread is attached to the outside of the casting mold wall, whereby an external thread matching the internal thread is formed on the outside of the outer conductor, in particular of the metal shield, whereby the outer conductor is screwed into the internal thread of the component. The component can be designed as a nut welded to the casting mold wall. The metal shield can be screwed into the internal thread. As a component, a screw nut can be welded to the outside of the metal mold, and the outside of the metal shield can be provided with an external thread matching the screw nut. The metal melt, the metal shield, the metal inner conductor and the metal mold have a high electrical conductivity and are therefore considered good electrical conductors.This screw connection prevents the coaxial cable from being ejected by the molten metal. The coaxial cable consists of a metal inner conductor and a dielectric. In a preferred embodiment, the coaxial cable also includes a metal shield. In an alternative embodiment, the outer conductor is formed by the conductive mold wall. A structural unit containing the dielectric and the inner conductor is arranged in the sensor holder. The coaxial cable is connected to an evaluation electronics unit. The evaluation electronics can detect the presence or absence of a molten metal. The complex reflection factor is preferably recorded as the measured variable. The stray capacitance C changes. ^when pouring in the molten metal and thus also the reflection factor, as will be described in more detail below. The method for detecting molten metal uses such a casting mold arrangement with at least one sensor device arranged in the casting mold wall. A transmission signal is sent to the sensor device and a reception signal is passed from the sensor direction to the electronics unit, wherein the presence or absence of the molten metal is detected by means of a change in the reception signal. In the preferred embodiment, a signal, in particular a continuous wave signal (CW signal), is generated by means of a synthesizer, wherein the signal is divided into two partial signals in a power divider ^ ^ ^ ^ ^ = ^ ^ ∙ cos ^ 2 ∙ ^ ∙ ^ ∙ ^ ^ with the same power, whereby one partial signal ^ ^ ^ ^ ^ = ^ ^ ∙ cos ^ 2 ∙ ^ ∙ ^ ∙ ^ ^is fed into the coaxial line via a circulator and forms the outgoing wave or the outgoing signal, where after reflection with the reflection factors ^ ^ or ^ ^ the partial signal is fed back into the electronic unit as a returning wave and the returning wave is separated from the forward wave by means of the circulator and is fed as ^ ^ ^^^ = ^ ^ ∙ cos^ ^2 ∙ ^ ∙ ^ ∙ ^^ + ∆!^ In particular, the signals ^ ^ ^^^ and ^ ^ ^^^ be mixed by means of a mixer, the mixed signal being filtered by means of a low-pass filter, the output signal thus obtained being ^ " ^^^ = ^ " = # $ ∙ cos^∆!^ is evaluated, in particular, using an oscilloscope. The frequency ^ is determined, preferably using the following calibration procedure: a) Calculate the maximum frequency ^ %&' , where the relative permittivity ( )*of the dielectric coating M1 a maximum value is assumed, with a highest frequency ^ %&' through the inner radius ^ & of the screen, the thickness D and the relative permittivity ( )* of the dielectric coating, where the smallest wavelength +%,-^^%&', ()*^ is determined by+%,-^^%&', ()*^ = / 01234 ∙ √678, where the phase velocity in vacuum is 9 ^ and satisfies the following two conditions s ind: b.) The frequency ^ of the synthesizer is set to the maximum frequency ^ %&' c) On an oscilloscope, the value for ^ "^ (=>>^: ^ " = ^ @^ ^ to be read and recorded d) Cover the opening of the coaxial cable with a conductor, especially an aluminum foil or aluminum sheet. e) On the oscilloscope, the value for ^"^ (ABCC DE^ F>^GCC −I9ℎD>CK>^: ^_# = ^_#A^ is read and recorded f) Calculate ∆^ " = ^ "^− ^ "^ g) If ∆^ " is too small: Reduce the frequency ^ and repeat steps c). h) If for all frequencies ^ the values ​​for ∆^ " are not satisfactory, replace the coaxial cable with a new one with a different length = MN&' and repeat steps b). The speed of the molten metal can be measured using two spaced-apart sensor devices. A first sensor device provides a first output signal and a second sensor device provides a second output signal, with these two output signals being fed to the two channels of a multi-channel oscilloscope, namely channel CH1 and channel CH2. First, the molten metal reaches the first sensor and the signal on channel CH1 changes its value, with the time O from now on. PQRRis measured until the value of the signal on channel CH2 also changes, this being the time at which the metal melt has reached the second sensor S2, the speed S T / U%QVWQ now knowing the distance = PQRR is calculated as follows: S T / U%QVWQ = =PQRR O PQRR The dimensioning of a coaxial cable and a corresponding sensor for detecting the molten metal in the mold can now be described as an example. A data sheet entitled "Coaxial Panel Connector" (Data Sheet 23_SMA-50-0-53 / 199_N, HUBER+SUHNER) describes a component with an inner conductor, a dielectric, and a mounting flange. This data sheet is referred to below as [3]. The paper [1] serves as the basis. 1. This publication deals with a coaxial cable whose outer radius of the inner conductor is G = 0.824DD and the inner radius of the shield is [ = 2.655DD. Since the outer radius of the inner conductor G = 0.824DD and the inner radius of the shield [ = 2.655DD do not necessarily correspond to the available dimensions of coaxial cables, expressions (8) and (9) from [1] must be analyzed. Furthermore, it is assumed that the coaxial cable has a characteristic impedance of ^_ = 50`. In [2] 2, the inductance per unit length = ^ and the capacitance per unit length a ^ the wave impedance of ^ _ calculated according to (1). (1) Where:c): Relative permeability of the dielectric(): Relative permittivity of the dielectric^&: Inner radius of the shield, in [m]^,: Outer radius of the inner conductor, in [m]^_: Wave impedance of the coaxial cable, complex quantity, in [Ω]As can be seen in (1), the wave impedance ^ _in addition to the material parameters of the dielectric also the ratio ^ & ⁄ ^ , A comparison between the data sheet [1] 1 for a "Coaxial Panel Connector" with wave impedance ^ _ = 50` and the information from [1] yields (2). (2) 3.22209 = 3.20313 It should now be assumed that the ratios from (2) correspond sufficiently accurately to (3). ( 3) [ ≈ G ^, Based on (3), the factors A & be defined according to (4): (4) 1.295 1 .288 With the relationships in (4), it can be assumed that the coaxial cable used in [1] is comparable to the "Coaxial Panel Connector" [1]. Therefore, it is justified that the following expression (5) should apply to the factor A. (5) [ = A = G ^ & ^, Now the expression (5) is applied to the equation (8) from [1] for the capacity a *, which will be presented here again (6), is applied. (6) With the substitution (7) we get (8) for the new capacity a *^ . (7) z = A ∙} → yz = A ∙ y}z^ = A ∙}^ → yz^ = A ∙ y}^ )3)3| ^ ^ ^ a * = 2 ∙ (^ ∙ ()* cos^x ^ ∙ y} ∙ y} ∙ yxs ln t^& j ∙ A ∙ www{^}^j + ^}^^j − ^2 ∙} ∙}^ ∙ cos^x^^^ ^, uv ) q ) q ^ The triple integral in (8) does not need to be recalculated, but the values ​​are already contained in Figures 2 and 3 in [1] (9). (9) )3)3| 2∙ ( ∙ ( cos^x^^ ∙ y} ^ ^ a *^ ^^ , , ^ & , A, ( )* ^ = ^ )* ∙ y} ∙ yxs ln t^& j ∙ w w w {^}^j + ^}^^j − ^2 ∙} ∙}^ ∙ cos^x^^^ ^, uv ) q ) q ^ a *^ ^^ , , ^ & , A, ( )* ^ = 1 A ∙ a * ^G, [, ( )* ^ Where the values ​​for a * ^G, [, ()* ^ are already included in Figures 2 and 3 in [1]. Analogously, for the capacity a j from [1]. In addition to (7), the substitution (10) also applies to the thickness y of medium 1. (10) where # now represents a new thickness. For the capacity a j applies according to [1] With the substitutions (7) and (10) the new capacity a results j^ (12): (11) ^ () - )3)3| 4∙ (^ ∙ ()* 1 − *∙ A ∙ ^ ^ ()j ^ cos^x^^ ∙ y} ∙ y}^ ∙ yx^ a j = sln t^& j ( uv )* ∙ ^w w w ^ -^* 1 + { ^}^j + ^}^^j + ^2 ∙ ^ ∙ #^j − ^2 ∙} ∙}^ ∙ cos^x^^^ ^, ()j ) q ) q ^ And here too (12) applies. The sum of the two capacities a * ^G, [, ( )* ^ and a j ^G, [, y, ( )* , ( )j ^ according to [1] the total capacity a^G, [, y, ( )* , ( )j^, which is graphically represented in [1] with Figures 2 and 3. Applied to (9) and (12), the final result (13) is obtained. ^E^.2 ^^y 3 E^ ^ 1 ^ : a ^ G, [, y, ()*, ()j ^ = a* ^ G, [, ()* ^ + aj ^ G, [, y, ()*, ()j ^ withNew total capacity: a^^^,, ^&, A, #, ()*, ()j^ = a*^^^,, ^& , A, ()*^ +aj^^^,, ^& , A, #, ()*, ()j^ a ^ ^ ^ , , ^ & , A, #, ( )* , ( )j ^ = 1 A ∙ a ^ G, [, y, ( )* , ( )j ^The analysis of the detector proposed here is based on Figures 1 and 2. These situations also correspond to Figures 2 and 3 in [1]. There are numerous possibilities for designing and developing the casting mold arrangement and the method. Preferred embodiments of the invention are now explained in more detail below with reference to the drawing and the associated drawing. The drawing shows: Fig. 1 in a schematic, sectional detail view of a casting mold arrangement with a first embodiment of a sensor device without melt, Fig. 2 in a schematic, sectional detail view of the casting mold arrangement with the first embodiment of a sensor device with melt, Fig. 3 an equivalent circuit diagram of an open-circuit coaxial cable, Fig. 4 a diagram in which the phase shift ∆^ is plotted as a function of the frequency ^ for dioxanes, Fig.5 is a diagram in which the phase shift ∆^ is plotted as a function of the frequency ^ for methanol, Fig. 6 is a schematic view of an electronic unit for carrying out the method, Fig. 7 is a schematic, sectional detail view of the casting mold arrangement with a second embodiment of a sensor device, Fig. 8 is a schematic, sectional detail view of the casting mold arrangement with a third embodiment of a sensor device, Fig. 9 is a schematic, sectional detail view of the casting mold arrangement with a fourth embodiment of a sensor device, and Fig. 10 is a schematic view of an arrangement for measuring the flow velocity. In Figs. 1 and 2, a casting mold arrangement 1 with a casting mold wall 2 and a coating M1 inside the casting mold wall 2 is shown in a detail.The casting mold wall 2 can also be referred to as a mold. The coating M1 is formed by a dielectric anti-adhesion layer and can also be referred to as medium 1. Depending on whether the casting mold arrangement 1 is filled with a melt or not, a layer with a medium M2 made of air (Fig.1) or in the form of a molten metal (Fig.2) is arranged on the inside, adjacent to the dielectric coating with the medium M1.c)* = 1 Relative permeability of the medium M1(. )*: Relative permittivity of the medium M1c)j = 1 Relative permeability of the medium M2()j: Relative permittivity of the medium M2The casting mold wall 2 has a sensor receptacle 3, wherein a sensor device is arranged in the sensor receptacle 3. The metal mold 2 is provided with a bore with a diameter of Ø^, wherein the bore forms the sensor receptacle 3. The sensor device can also be referred to as a sensor. The sensor device has an idle coaxial line 4 with an open end, wherein the coaxial line 4 has an inner conductor 5 arranged in the sensor receptacle 3 of the casting mold wall 2 and a dielectric 7 extending between the inner conductor 5 and an outer conductor 6. The outer conductor 6 is formed by a metal shield 8. By rotating the metal shield 8 about its own axis, the coaxial cable can be guided into the bore until the end face of the coaxial cable has reached the end of the bore.The outside of the metal shield 8 is provided with a thread 10. The sensor device shown in Figs. 1 and 2 has the task of detecting the presence of a metal melt M2. The metal melt M2, the metal shield 8, the metal inner conductor 5 and the metal mold 2 have a high electrical conductivity and are therefore considered good electrical conductors. The outer diameter of the metal shield 8 is dimensioned such that the metal shield 8 can be easily inserted into the sensor holder 3, namely the bore. Furthermore, a nut 9 is welded to the outside of the metal mold 2 by means of a weld seam 9.1 and the outside of the metal shield 8 is provided with a thread 10 matching the nut 9. This screw connection prevents the coaxial cable 4 from being expelled by the metal melt.To secure the coaxial cable 4, in a preferred embodiment, a heat-resistant adhesive is applied between the metal shield 8 and the sensor receptacle 3. In addition to securing it, the adhesive also functions as a sealant, preventing the molten metal from flowing toward the nut 9. The same adhesive is used to secure the metal inner conductor 5 to the dielectric 7, and the dielectric 7 to the inner surface of the metal shield 8, again fulfilling the two functions of securing and sealing. By applying an adhesive between the metal inner conductor 8 and the bore of the dielectric, the desired thermal conductivity can be achieved depending on the value of the relative permittivity (λ). )The cured adhesive can change the wave impedance. Since only the change in the phase of the reflection factor is significant, the single wave impedance change is tolerable within certain limits. It is sufficient that the phase changes clearly and measurably in the empty and filled state of the mold. Furthermore, the dielectric can be pressed into the coaxial cable 4 so that it is held in place purely by friction; then, no adhesive is required within the coaxial cable 4. The reflection factors serve as the measured variable. and ^ ^ according to (14) and (15) according to [2] with the equivalent circuit of the sensor according to Fig.3. For the equivalent circuit in Fig. 3, the following applies:^_ = ^_ = 50Ω^G^GKE^ä^ ED C>>^>D ^^^^G^y ^G9ℎ ^E^^^ 1: a^ = a^^^G^GKE^ä^ DE^ F>^GCC − I9ℎD>CK> ^G9ℎ ^E^^^ 2: a^ = a^^( 14) ^^ : Empty state according to Figure 1: ^^ : With metal melt according to Figure 2: Where ^ denotes the frequency in Hz and ^ the imaginary unit. In the following, the arguments ! ^ = G^^ ^ ^ ^^ and ! ^ = G^^ ^ ^ ^^ the complex reflection factors ^ ^ and ^ ^ be considered (16), (17). ( 16) !^ = G^^^^^^ : Empty state according to figure 1:^^ = 1 ∙ >^^∙^^^^∙^^ = >^^∙j∙^^! ^ = G^^^^ ^ ^ = arctan ^ 2 ∙ ^ ∙ ^ ∙ a ^^ ∙ ^ _ ^ ; 0 ^Gy ≤ ! ^ ≤ ^ ⁄ 2 ( 17) ! ^ = : With metal melt according to Figure 2: ! ^ = G^^ ^ ^ ^^ = arctan^2 ∙ ^ ∙ ^ ∙ a ^^ ∙ ^ _ ^ ; 0 ^Gy ≤ ! ^ ≤ ^⁄ 2 The difference angles ∆ are now important! ^ and ∆! ^ according to (18) and (19). (18) Where the phase angle ! ^should serve as a reference. The phase shift ∆^ according to (20) should be considered as the figure of merit. (20) This parameter describes the phase shift when the molten metal is poured in. The choice of frequency must ensure that no ambiguities arise, ie, condition (21) must be met: ( 21) ^>yE^^^^^ ∶ !^ ≠ !^ As an example, the data from [1] are to be used. It is assumed that the relative permittivity of the "anti-stick" solution is between that of methanol (( )* = 33.1^ and that of Dioxane (( )*= 2.1^. Furthermore, a layer thickness (thickness of the "anti-adhesion" solution film) of # = 0.1DD is assumed. Using the calculation rules (5) and (10), the values ​​of the capacitance a^G, [, y, ()*, ()j^ can be determined graphically from Figures 2 and 3 of [1]. Table 1 summarizes the results. The dimensions of the coaxial cable should be taken from the data sheet [1]. Taking mechanical tolerances into account, the factor A can now be derived (22). ( 22) [ ^ = A = G ^≈ 1.29 → ^>^^^>^K^^^ SB^ A: A = 1.29 & , From this, with the help of (10), the thickness y, which is plotted as the x-axis in Figures 2 and 3 from [1], can be determined (23). ( 23) y= A ∙ # = 1.29 ∙ 0.1DD = 0.129DDSummary D ioxane Methanol ()* 2.1 33.1# 0.1mm 0.1mmA 1.29 y according to (10): y = A ∙ # 0.129mm 0.129mmFigure 2, [1] for air: 0.04 ∙ 10 ^*j ^ 0.2 ∙ 10 ^*j ^ a ^ G, [, y, ()* , ( )j ^ Figure 3, [1] for metal:0.6 ∙ 10 ^*j ^ 10 ∙ 10 ^*j ^ a^G, [, y, ()*, ()j^Table 1: Summary of the values ​​To determine the appropriate frequency range for the frequency ^ the graphical representations Fig.4 and 5 are used. The highest frequency ^ %&' is determined by the inner radius ^& of the screen, the thickness D and the relative permittivity()* of the medium 1. The smallest wavelength +%,-^^%&', ()*^ in medium 1 is determined by (24). (24) With the phase velocity 9 ^ in vacuum. In order to use the capacity a calculated in statics, all considerations must be carried out in quasi-statics. This leads to conditions (25) and (26): ( 25) Calculated, this results in: Using the values ​​from [1] we get: This results in the highest frequency ^ %&' to : ^ %&'= 1£¢K. CALCULATION: Dioxane D = 0.1 [mm] Empty: C_VL = 3.10078E-14 [F] With metal: C_VV = 4.65116E-13 [F] π = 3.141592654 [-] Empty: 2 * π * C_VL * Zw = 9.74137E-12 [s] With metal: 2 * π * C_VV * Zw = 1.46121E-10 [s] CALCULATION: Methanol D = 0.1 [mm] Empty: C_VL = 1.55039E-13 [F] With metal: C_VV = 7.75194E-12 [F] π = 3.141592654 [-] Empty: 2 * π * C_VL * Zw = 4.87069E-11 [s] With metal: 2 * π * C_VV * Zw = 2.43534E-09 [s] For the precise frequency determination, the setup in Fig. 6 is considered. Fig. 6 shows the signal processing concept. A synthesizer 11, a power divider 12, a circulator 13, a mixer 14, and a low-pass filter 15 are located in a housing 16 and form the electronics unit 16. The electronics unit 16 is firmly attached to the mold 2 at a defined distance via a rigid connection 17. Care should be taken to ensure that the heat flow from the mold 2 to the electronics unit is as minimal as possible.Synthesizer 11 generates a continuous wave (CW) signal, which is split into two signals with the same power in power divider 12. One signal is fed via circulator 13 into coaxial line 4 and forms the outgoing wave or signal 18. After reflection, it has the reflection factors. or ^ ^ The signal is fed into the electronic unit 16 as a returning wave 19. The circulator 13 separates the returning wave from the forward wave and is called ^ ^ ^ ^ ^ denoted by (27). Where ^ is the time. ( 27) ^^^^^ = ^^ ∙ cos^ ^2 ∙ ^ ∙ ^ ∙ ^^ + ∆!^ mit: ^^: Amplitude, real, in volts^: Frequency, in Hz^: Time, in s∆!: Phase angle, in rad :∆! = ∆!^ = !^^^^ − ^2 ∙ !^^ or ∆! = ∆! ^ = ! ^ ^^^ − ^2 ∙ ! ^ ^!^^^^: Phase angle, in radians, referred to the signal ^^^^^ = ^^ ∙ cos^ 2 ∙ ^ ∙ ^ ∙ ^^So that the phase angle ! ^ ^ ^^ In order to maintain the constant phase angle when empty and with molten metal, the coaxial line or cable from the electronics unit 16 to the mold 2 must be rigid, ie, the shield 8 consists of a solid tube and not a flexible braid. The phase angle ! ^ ^^^ depends on the frequency ^ and the coaxial cable length = MN&' , as well as the elements in the path. Furthermore, the coaxial cable length = MN&' be as short as possible. The signals ^ ^ ^^^ and ^ ^ ^^^ are fed to a mixer 14, followed by a low-pass filter 15. The output signal ^ " ^^^ according to (28) is led out of the housing via an electrical connection and fed to an oscilloscope 20. (28) ^ " ^ ^ ^ = ^ " = # $ ∙ cos ^ ∆! ^ mit #$: Amplitude, real, in volts∆!: Phase angle, in radians :. ∆! = ∆! ^ = ! ^ ^ ^^ − ^ 2 ∙ ! ^ ^ or ∆! = ∆! ^ = ! ^ ^ ^ ^ − ^ 2 ∙ ! ^ ^ The oscilloscope 20 monitors the course of the signal ^ " ^^^ = ^ " . In the empty state, the signal is measured according to (29). ( 29) =>>^: ^"^^^ = ^"^ = #$ ∙ cos^!^^^^ − ^2 ∙ !^^^And when the mold 2 is filled with the metal melt, the signal changes to (30) ( 30) FE^ F>^GCC − I9ℎD>CK>: ^"^^^ = ^"^ = #$∙ cos^!^^^^ − ^2 ∙ !^^^The presence of a metal melt is thus only detected via a signal change ∆^" (31).( 31) From equation (28) it can be seen that ambiguities (32a) and (32b) can occur. With ^ = ⋯ , −3, −2, −1, 0, 1, 2, 3, … and D, ^ = 1, 2, 3, … we get: From the ambiguities (32a) and (32b), the conditions A …C, (33a) … (33c) can be derived. From (32a) the following conditions follow: Condition A (33a) can now be applied to Figures 4 and 5. All values ​​must be converted to degrees instead of radians. This yields (34). (34) ∆^, ^°^ 3 60° ∆^, ^°^ = 180° ^ ∙ ∆^ As can be seen in Figures 4 and 5, (34) is satisfied for frequencies less than or equal to 1 GHz, since ∆^, ^°^ < 360°. Conditions B and C can only be satisfied in practice, since the phase angle ! ^ ^^^ is known depending on the setup. To determine the frequency ^, the following calibration procedure can be used to find the optimal frequency ^: 1. Calculate the maximum frequency ^ according to (24), (25) and (26). %&' , where the relative permittivity ( )* the "anti-stick" solution is set to a maximum value. 2. The frequency ^ of the synthesizer is set to the maximum frequency ^ %&' 3. On the oscilloscope, the value for ^ "^to read and record 4. Cover the opening of the coaxial cable with aluminum foil or aluminum sheet. 5. On the oscilloscope, the value for ^ "^ to read and record 6. Calculate ∆^ " = ^ "^ − ^ "^ 7. If ∆^ " is too small: Reduce the frequency ^ and repeat steps 3 and 4. If for all frequencies ^ the values ​​for ∆^ " are not satisfactory, replace the coaxial cable with a new one with a different length = MN&'and repeat the steps from no. 2. Fig. 7 shows a second embodiment of the sensor device. A sensor receptacle 3 in the form of a threaded hole has been machined into the mold 2. The sensor receptacle 3 here has an internal thread 22. The internal thread 22 can extend over the entire length of the sensor receptacle. The metal shield 8 has a continuous external thread 10. By screwing, the coaxial cable is screwed into the mold 2 until the end face reaches the end of the threaded hole. The lock nut 9 fixes the coaxial cable 4 and thus firmly connects it to the mold 2. No adhesive is required for fixing. However, an adhesive can again take on the function of a seal, as described with regard to the first embodiment of the sensor device (see description of Figs. 1 and 2). The same comments regarding the change in wave impedance in the presence of an adhesive apply as explained above.In one embodiment of this second sensor device, the adhesive can be omitted. In this case, it is possible that the liquid metal melt can penetrate into the space between the inner surface of the metal shield and the outer surface of the dielectric, as well as into the space between the inner surface of the dielectric and the outer surface of the metal inner conductor. The melt will cool and thus solidify and remain in the spaces. During subsequent casting processes, the metal residue may possibly change its state of aggregation again and possibly flow even more into the spaces. Since here a very thin layer of the solidified / liquid metal melt is used compared to the inner radius of the shield ^. & and the outer radius of the inner conductor ^ ,is calculated and this is a metal melt and thus a material with good electrical conductivity, the change in wave impedance is small. After a certain number of casting processes, the penetration depth should no longer change and the wave impedance jump between areas with and without penetrated metal melt remains constant over time. Here too, only the phase change of the reflection factor is important, i.e. only the measurement before filling and after filling with the metal melt. In this way, the change in wave impedance from measurement to measurement can be taken into account. Fig. 8 shows a third version of the sensor device. Version 3 uses a design as available in [1]. In this case, a structural unit consisting of the inner conductor 5, the dielectric 7 and a connecting flange 23 with the inner conductor 5 and the dielectric 7 is arranged in the sensor holder 3.The connecting flange 23 is fastened to the outside of the casting mold wall 2 outside the sensor receptacle 3. The sensor receptacle 3 is in turn formed by a bore. The diameter of the sensor receptacle 3 corresponds to the outer radius of the dielectric 7. As can be seen in Figure 8, the inner wall of the sensor receptacle 3, i.e. the bore in the mold 2, takes on the function of the metal shield (not designated in more detail here). This also creates a coaxial line 4. The connecting flange 23 has an external thread 24, wherein the electronics unit or another rigid connection can be connected to the external thread 24. The connecting flange 23 further has a flange plate 25, which rests on the outside of the mold 2 and is screwed to it with at least one screw 26. Fig. 9 shows a fourth embodiment of the sensor device.This fourth design is suitable for applications in which the molten metal is pressed into the mold 2 at high pressure. The diameter of the sensor holder 3 and also the diameter of the sensor device arranged therein expands from the outside to the inside of the mold 2. The sensor holder 3 is conical and the coaxial cable 4 has a truncated cone shape or cone shape within the sensor holder 3. The conical design of the coaxial cable 4 distributes the forces on the metal mold 2 and prevents the coaxial cable 4 from being pushed out. The aim is for the wave impedance Z to be ­Due to the shape of the section between the cone and the cylindrical coaxial cable, impedance jumps are avoided as much as possible, resulting in a reflection factor that is as low as possible due to the transition. It is generally assumed that the wave impedance in the conical coaxial cable differs from the wave impedance of the cylindrical coaxial cable. The fact that the wave impedance changes along the coaxial cable does not contribute to the functionality, since only the signal change between the "empty" and "full" states is important. An additional nut 9 fixes the coaxial cable 4 and prevents it from being torn out when the cast workpiece is removed. Given the expanding shape in the form of a cone or other geometry, i.e.that the extent of the coaxial cross-section / end face facing the molten metal is larger than the cross-section of the coaxial cable outside the metal mold, the coaxial cable 4 is pressed into the tapered inner surface of the sensor receptacle 3 of the metal mold 2 by turning the nut 9. This fixes the coaxial cable 4. It is conceivable that an adhesive is used. The adhesive that is possibly used only performs the function of a seal. The same comments apply with regard to the adhesive and with regard to the penetration of the molten metal into the gaps as for the first two versions of the sensor device. Fig. 10 shows an arrangement for measuring the velocity of the melt with two sensor devices S1 and S2 spaced apart in the direction of flow. With the arrangement of the sensor devices S1 and S2, the velocity of the molten metal can be measured. The sensor device S1 supplies a first signal.Sensor device S2 provides a second signal. These two output signals are fed to the two channels of a multi-channel oscilloscope, channel CH1 and channel CH2. First, the molten metal reaches sensor S1. The signal on channel CH1 changes its value. From now on, the time becomes 0. PQRR measured until the value of the signal on channel CH2 also changes. This is the point in time at which the molten metal reaches the sensor S2. The speed S T / U%QVWQ can now, knowing the distance = PQRR can be calculated using (35). (35) S T / U%QVWQ = =PQRR O PQRR

[0002] List of reference symbols: 1 Casting mold arrangement 2 Casting mold wall / mold 3 Sensor holder 4 Coaxial line / coaxial cable 5 Inner conductor 6 Outer conductor 7 Dielectric 8 Metal shield 9 Nut 9.1 Weld seam 10 Thread of the metal shield 11 Synthesizer 12 Power divider 13 Circulator 14 Mixer 15 Low-pass filter 16 Housing / electronics unit 17 Rigid connection 18 Transmitted signal / outgoing signal 19 Returning signal 20 Oscilloscope 21 Power supply 22 Internal thread 23 Connecting flange 24 External thread 25 Flange plate 26 Screw M1 Dielectric coating / medium 1 M2 Layer of air or molten metal / medium 2 S1 First sensor / first sensor device S2 Second sensor / second sensor device CH1 First channel of the oscilloscope CH2 Second channel of the oscilloscope

Claims

Patent claims:

1. Casting mold arrangement (1) with a casting mold wall (2) and at least one sensor device for detecting the presence of a molten metal in the casting mold arrangement (1), characterized in that a dielectric coating (M1) is arranged at least on a part of the inside of the casting mold wall (2), wherein the sensor device (S1, S2) has an open-circuit coaxial line (4) with an open end, wherein the coaxial line (4) has an inner conductor (5) arranged in a sensor receptacle (3) of the casting mold wall (2) and a dielectric (7) extending between the inner conductor (5) and an outer conductor (6), wherein the open end of the coaxial line (4) borders the dielectric coating. 2.Casting mold arrangement according to claim 1, characterized in that a component with an internal thread is fastened to the outside of the casting mold wall (2), wherein an external thread (10) matching the internal thread is formed on the outside of the outer conductor (8), wherein the outer conductor (6) is screwed into the internal thread of the component.

3. Casting mold arrangement according to one of the preceding claims, characterized in that the component is designed as a nut (9) welded to the casting mold wall (2).

4. Casting mold arrangement according to one of the preceding claims, characterized in that the sensor receptacle (3) is formed by a bore.

5. Casting mold arrangement according to one of the preceding claims, characterized in that the diameter of the sensor receptacle (3) and also the diameter of the sensor device arranged therein widen from the outside to the inside of the casting mold wall (2). 6.Casting mold arrangement according to one of the preceding claims, characterized in that the coaxial line (4) is designed as a coaxial cable (4) with. a metal shield (8), wherein the metal shield (8) is arranged and, in particular, fastened in the sensor receptacle (3).

7. A casting mold arrangement according to one of the preceding claims, characterized in that a structural unit consisting of the inner conductor (5), the dielectric (7), and a connecting flange with the inner conductor (5) and the dielectric (7) is arranged in the sensor receptacle (3), wherein the outer conductor is formed by the conductive casting mold wall (2).

8. A method for detecting a molten metal in a casting mold arrangement, in particular according to one of the preceding claims, wherein the casting mold arrangement has a casting mold wall (2) and a sensor device (S1, S2) arranged in a sensor receptacle (3) of the casting mold wall (2), wherein a transmission signal is sent to the sensor device (S1, S2) and a reception signal is passed from the sensor device to an electronic unit (16),wherein the presence or absence of the molten metal is detected by means of a change in the received signal, characterized in that the sensor device (S1, S2) has an open-circuit coaxial line (4) with an open end, wherein the coaxial line (4) has an inner conductor (5) arranged in a sensor receptacle (3) of the casting mold wall (2) and a dielectric (7) extending between the inner conductor (5) and an outer conductor (6), wherein the open end of the coaxial line (4) is adjacent to the dielectric coating (M1), wherein a transmission signal (18) with a frequency f is applied to the coaxial line (4) by means of the electronics unit (16), wherein the signal (19) returning from the coaxial line (4) is evaluated by means of the electronics unit (16).

9. A method for detecting a molten metal in a casting mold arrangement, in particular according to one of the preceding claims,wherein the casting mold arrangement comprises a casting mold wall and at least one sensor device (S1, S2) arranged in the casting mold wall, wherein a transmission signal is sent to the sensor device (S1, S2) and a reception signal is passed from the sensor direction to an electronic unit (16), wherein the presence or absence of the molten metal is detected by means of a change in the reception signal, characterized in that characterized in that a signal, in particular a continuous wave signal (CW signal), is generated by means of a synthesizer (11), wherein the S ignal in einem Leistungsteiler (12) in zwei Teilsignale ^^^^^ = ^^ ∙ c os^ 2 ∙ ^ ∙ ^ ∙ ^^ mit derselben Leistung aufgeteilt wird, wobei das eine Partial signal ^ ^ ^ ^ ^ = ^ ^ ∙ cos ^ 2 ∙ ^ ∙ ^ ∙ ^ ^ is guided via a circulator (13) into the coaxial line (4) and forms the outgoing wave or the outgoing signal (18), wherein after reflection with the reflection factors ^ ^ or ^ ^the partial signal is fed back into the electronic unit (16) as a returning wave (19) and by means of the circulator (13) the returning wave is separated from the forward wave and is fed back as ^ ^ ^ ^ ^ = ^ ^ ∙ cos ^ ^ 2 ∙ ^ ∙ ^ ∙ ^ ^ + ∆! ^ 10. Method according to the preceding claim, characterized in that the signals ^ ^ ^^^ and ^ ^ ^^^ are mixed by means of a mixer (14), and the mixed signal is filtered by means of a low-pass filter (15), the output signal thus obtained ^ " ^^^ = ^ " = # $ ∙ cos^∆!^ is evaluated, in particular by means of an oscilloscope (20).

11. Method according to one of the preceding claims, characterized in that the frequency ^ is determined by the following calibration rule: a) Calculate the maximum frequency ^ %&' , where the relative permittivity ( )*of the dielectric coating M1 a maximum value is assumed, with a highest frequency ^ %&' through the inner radius ^ & of the screen, the thickness D and the relative permittivity ( )* of the dielectric coating, where the smallest W ellenlänge +%,-^^%&', ()*^ durch is determined, where the phase velocity in vacuum is 9 ^ denotes w ird und die folgenden beiden Bedingungen erfüllt sind: b) The frequency ^ of the synthesizer is set to the maximum frequency ^ %&' set. c) On an oscilloscope, the value for ^ "^ to read and record d) Cover the opening of the coaxial cable with a conductor, especially an aluminum foil or aluminum sheet. e) On the oscilloscope, the value for ^ "^ read and recorded f) Calculate ∆^ " = ^ "^ − ^ "^ g) If ∆^ "is too small: Reduce the frequency ^ and repeat steps c). h) If for all frequencies ^ the values ​​for ∆^ " unsatisfactory s ind, wechsle die Koaxialleitung durch eine neue mit veränderter Länge = MN&' aus und wiederhole die Schritte ab b).

12. Method according to one of the preceding claims, characterized in that by means of two mutually spaced L Mess arranged sensor devices (S1, S2) designed according to one of the preceding claims, the speed of the molten metal is measured.

13. Method according to the preceding claim, characterized in that the sensor device (S1) provides a first output signal and the sensor device (S2) provides a second output signal, wherein these two output signals are fed to the two channels of a multi-channel oscilloscope, namely channel CH1 and channel CH2, wherein first the molten metal reaches the first sensor S1 and the signal on the first channel CH1 changes its value, wherein from now on the time O PQRRis measured until the value of the signal on the second channel CH2 also changes, this being the time at which the metal melt has reached the second sensor S2, where the speed S T / U%QVWQ now knowing the distance = PQRR is calculated as follows: S T / U%QVWQ = =PQRR O PQRR

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