MXPA99004298A

MXPA99004298A - Metering oven

Info

Publication number: MXPA99004298A
Application number: MXPA/A/1999/004298A
Authority: MX
Inventors: Malpohl Klaus
Original assignee: W Strikfeldt & Koch Gmbh 51674 Wiehl De
Priority date: 1996-11-11
Filing date: 1999-05-07
Publication date: 2000-06-01

Abstract

The invention concerns a metering oven (1) with a vessel (12) for holding a liquid metal and with a device for detecting a liquid metal level in a vessel. A tubular probe (5) is connected to a gas source (10) for discharging a gas at a predetermined pressure from the gas source through the probe and out of its outlet aperture. The probe is spatially associated in a fixed manner with the vessel such that pressures which can be detected by a pressure-measuring device (9) can be associated with different liquid metal levels inside the probe. At a given pressure threshold value, the pressure-measuring device can emit a signal for a given liquid metal level to be detected.

Description

DOSAGE OVEN DESCRIPTION OF THE INVENTION: The invention relates to a dosing oven with a container for receiving fluid metals and a device for covering a liquid metal capacity in a container. For the metering of liquid metal from a dosing furnace the metal column rising in the dosing tube must be encompassed in its height, since the dosage amount is calculated by that span. It is also possible, depending on the acquisition of the height of the metal column taking into account another parameter, for example different pressures, to determine the height of the level or capacity of liquid in the furnace. US 4 220 319 discloses a sensor arrangement for a dosing furnace, in which the sensor consists of a metal needle that is vertical or almost vertical to the surface of the metal, and which, upon contact with the surface of the liquid metal, emits a signal . To decrease the wear of the sensor arrangement, the metal needle is weighed away from contact with the metal surface by means of an automated mechanical system. This known arrangement has different disadvantages, especially that the mechanical tilting system is very complicated and expensive and despite tilting the wear on the needle is relatively large. The needle can firstly contact with the liquid aluminum due to the chemical process decomposing.

REF .: 30153 In addition the. The result of the measurement is influenced by the formation of layers of aluminum or aluminum oxide on the needle. In practice due to the wear of the metallic needle explained above, sharpening, cleaning or changing the needle is necessary, so that the palpation position can not be maintained for a long period of time. Also, in practice, you do not know auxiliaries and adjustment, which would allow a reproduction of the palpation. Especially in the dosing furnaces, the palpation position with respect to the outlet edge of the dosing tube has an important significance. The needle should, for a reproducible dosage, cover or pick up the exact position of the liquid metal on the outlet side of the dosing tube (the needle and the exit edge should be seated at the same height). The embracing in practice not only of displacement for maintenance and placement of the metallic needle but also by the change of the dosing tube whose installation height directly determines the position of the exit edge. Being conditioned by large manufacturing technical tolerances in the area of firm fire the introduction of a new dosing tube as well as a new sealing etc, moves the output edge up to 10mm in perpendicular height.

In the dosing furnaces, it causes a displacement in the palpation position in relation to the exit edge by the previous measurements of, for example, 5 mm, a variation of. that of the metal metered typically of 4% It demands a accuracy of dosage of 1 to 2%. Because of the difficult reception or entry and heat, which prevails in the area of palpation, in reality the needle is not adjusted, but the parameters of pressure and time of the dosage or according to us the dosage weight, which is determined by the integral method (pressure in time) is varied, to compensate for the false weight of dosage. This has the disadvantage that strainers that have stored dosing parameters of different castings must always make new corrections of those stored values, since the palpation ratios and with this the dosing does not remain constant. Another disadvantage of the aforementioned metal guide is (due to the necessary contact with fluid metal melt) the conditioning of the principle. A layer that forms on the surface of the metal melt after a short time, in general, of non-conductive aluminum oxide, must be broken first by the needle. As a result of the pressure of the needle there is a bulging of the metal surface downwards. This first results in an inaccurate measurement result (the needle gives its signal after the break in too deep a position), that is, it shows less metal melt than actually exists. In addition, after the breakage of the oxide surface, the needle is unnecessarily deep-seated in the fluid metal melt, so that the wear described above of the metal needle accelerates. DE-OS 4420 712 discloses a sensor arrangement for capturing the gauging of the fluid metal, in which the sensor consists of an electrically conductive ceramic and this post is attached to the wall of the container or in an inclined or ascending pipe. . As a determining state of the state of the art, JP-A-0 5099726 is considered. This presents a tube opened towards the interior of a casting tray, which is arranged in the wall of the casting tray filled with metallic flux, where the tube opening is below the upper level of the fluid metal flux. Gas is blown from the tube onto the melt. Which produces a back pressure in the metallic flux (by means of which the full height of the metallic flux can be deduced) which can be captured by a pressure measuring device in the tube. For the measurement of an exact filling height, which would meet the requirements of a dosing furnace, a complicated pressure measurement installation would be necessary here, which in addition to the high cost would require a continuous calibration. The invention proposes the task, to create a dosing oven with a container for receiving fluid metal and a device for capturing a fluid or liquid metal capacity in the container, where the device accurately captures a predetermined capacity. This task is solved according to the invention by the characteristics of the main claim in relation to the characteristics of the introductory idea. In this way, the pressure measuring device is realized as a pressure wave switch to encompass or capture a pressure reaction wave inside the probe and produce a corresponding signal, when the opening of the probe is closed by the liquid metal , and the probe is fixedly fixed on the wall of an ascending tube arranged in the wall of the container, a simple device is produced to capture the capacity of the liquid metal, which has an economic cost and nevertheless captures with a good accuracy a capacity predetermined. In contrast to the method mentioned at the beginning, which is based on an electrical contact, in the present device, for example, no earthing is needed. the indirect measurement by means of a gas (the intermediate switching of the gas minimizes the direct contact between the probe and the metal melt, and the very thin deposits in the probe do not show any marked influence on the gas current ratio) based on a wear-free system and firmly structured, it shows the other advantage that the distance relationships remain constant. On the one hand, the height of the palpation position of the ceramic tube (fixedly installed, nor its position with respect to the outlet edge (fixedly installed) does not change.) This means that the distance ratios remain constant, even if the dosing tube It is too high or too deep in the dosing furnace, and the possibility of falsification of the measured value due to a change in the electric conductivity over time (as in the electric conductive ceramic sensor mentioned above) is excluded. By means of the measures given in the subclaims, other advantageous embodiments and improvements are possible.The tube or the probe can be fixed on the wall or in a stopped tube of a dosing furnace., when passing the capacity of liquid in the stopped tube, the desired signal is presented. Preferably the ceramic probe consists, as this leads to the fact that the possibility of deposits of metal in the probe become minimal (especially in the pair of ceramic / aluminum materials). If thin deposits are present anyway (in part because of the roughness of the probe) in the probe according to the present invention, this does not lead to a disturbance of operation, whereas the measurement system, which is based on a electric contact, can already cause thin deposits, a complete precipitation. It is especially advantageous to provide the probe made of ceramic with an internal diameter less than 2 ram. Due to the established surface tensions, some fluid aluminum on the ceramic, the probe 9 remains in a permanent gas stream without being enclosed in the fluid aluminum. Another advantageous embodiment is provided, because the device for pressure measurement has a pressure wave switch adjustable in pressure sensitivity to measure a reactant wave at the pressure of a gas flowing from the probe. The reaction wave at the pressure that occurs when the probe reaches or closes at a level of liquid metal, is used, for example, as a signal to close a feed valve in the dosing furnace. The adjustability of the pressure wave switch allows the easy determination, even possible during operation, of the relationships of the corresponding installation location.

Another advantageous embodiment will be sought, because the dosing oven has several devices for capturing a gauging of fluid metal, which have respective probes with an exit opening. When these outlet openings (in reference to a metal gauge at rest of the liquid metal) are next to each other, then in the case of a movable surface of the liquid metal in the gauge by appropriate formations of the average value, cover the pressures measured by the probe, leaving these outlet openings one above the other, thus being possible to obtain the state of filling in broad limits. An exemplary embodiment of the invention is shown in the drawing and will be explained in detail below. Sample: Figure 1 schematically a section through a dosing oven with standing or rising tube; 2 shows an enlarged partial section of the end of the tube-shaped probe placed on the wall of the stopped tube. Figure i shows a dosing furnace l with a container 12, in which a fluid metal, for example aluminum, is received in a tub 2. In the dosing furnace l a standing pipe 3 is placed, which is led outwards through the wall 4 of the dosing furnace 1. Liquid metal is dosed through the riser 3. This can be done approximately (after the measurement by a sensor device) by the regulated application of pressure inside the container 12, to drive the liquid metal inside the riser 3 to an outlet pipe 13. The pipe of outlet 13 filled with the metal melt, preferably aluminum, the casting molds provided for this purpose. Here, it is important that the amount of metal melt extracted from the container 12 is determined by the volume of the casting mold. For the output dosing it is necessary that the height of the metal column in the dosing furnace (or in the riser 3) is accurately captured, where a pneumatic sensing device is used for that pick-up. The pneumatic sensor device has a probes constructed as a tube 5, which preferably consists of ceramic, and according to FIG. 2 is placed on the wall of the rise tube 3. For this purpose, for example, a perforation 8 is provided. as stepped perforation in the wall 7, where the drilling part with a larger diameter is pressurized or the end of the probe 5 is fixed from the outside in the wall of the rising tube 7, and where the smallest diameter of the perforation in step 8 corresponds approximately to the internal diameter of the tube 5. The probe 5 is connected by a pressure measuring device 9 to a gas source 10. The gas source supplies gas with a determined pressure to the probe 5, which flows outward from the front end and through the bore 8. If the level of metal in the riser tube approaches the end of the probe, the current ratios at the end of the probe vary and occur a pressure variation in the probe. This variation of pressure is determined by the pressure measuring device 9. This is an indirect procedure to measure the state of the gauge, since the gauging state must be performed in a non-direct way (what would be the touch with an element of contact provided for it). Instead, the influence of a metal gauging is obtained, which is to be measured on given current ratios (of a gas leaving a tributary of gas to flow with a defined pressure). This influence can be determined by means of a pressure variation of the gas flowing outwards in the probe 5. By means of this pressure variation, information on the capacity of the fluid metal is also made possible. A particularly clear measurable pressure variation occurs, if the open end of the probe 5 (or bore 8) is closed by the fluid metal. To be able to accurately capture the capacity of the fluid metal, before the own measurement, the pressure curve is measured in the approximation by the rise of the gauge and a pressure threshold value is determined, where the gauge presents a predetermined coordination to the end of the probe 5. The measuring device of pressure 9 then gives a corresponding signal at its output to the other evaluation, control / regulation apparatuses. A measuring device for measuring the pressure in the tube 5 is suitable as a pressure measuring device 9. For example, a bridge switching can be used, wherein two cross-sectional throttling sections are connected in a parallel switching with the source of the pressure. gas 10. The outlet of the first throttle is connected with a cross section of variable throttle and the outlet of the second throttle with the probe 5. Between the outlets of the first and second throttles in its fixed cross sections there is a measuring piston , which varies in position according to the pressure tilts. By adjusting the variable throttle, the measuring system can be set in such a way that the pressure is essentially present on both sides of the measuring piston. If the current ratios or proportions vary in the tip of the probe 5, this is in the perforation 8, due to the approach or distance of the metal level, the position of the measuring piston will vary, with which information about the existing pressure. The position of the measuring piston can be captured, for example, by a Reed contact. In another mode, a so-called pressure wave commutation is used. whose zone of adjustment is approximately between 0.5 and 5 mbar. These switches have a membrane inside, where a contact is placed. One side of the membrane is exposed to ambient pressure, the other side is connected to the probe tube or probe 5. Yes. Now the probe tube 5 is closed by a liquid, the pressure in the tube 5 increases and with this one side of the membrane and this will be pressed against an electrical contact that is fixed, so that the electrical contact on the membrane enters the membrane. contact with the one that is fixed. This produces a current flow upon reaching the reaction wave at the pressure. The establishment of pressure sensitivity is easily accomplished by adjusting the distance of the fixed electrical contact to the membrane with the help of a screw, which is provided with a scale. Depending on the position of the screw, the fixed electrical contact will be more or less removed from the electrical contact placed on the membrane so that more or less pressure will need to be applied to touch both contacts. Since, it is possible that during a dosing process from the container 12 or the rising tube 3 and the outlet pipe 13 to a casting mold it is possible to reach a closed or capped hole 8 or the probe 5, a protection against that covering of the openings has been provided. This is primarily caused by a dynamic pressure caused by the gas source, which in closing the opening 8 takes care that the probe does not run completely filled with metal melt. In addition, it is possible with an adequate selection of materials of the probe or of the surrounding or component parts thereof (riser tube, a section of the container wall) to greatly prevent the deposition or adhesion of molten metal. With the selection according to the invention of an internal diameter of the probe 5 or of the perforation made as connection hole 8 smaller than 2 mm and a suitable pair of materials (ceramic for the parts of the probe 5 that come in contact with the metal melt and the construction part containing the connection hole 8, in this case the riser tube 3) makes it difficult to plug or close the metal melt. Due to the surface tensions that are adjusted by the parts of certain materials, approximately between the ceramic and the liquid aluminum, a plugging is completely excluded. This has a decisive significance for the present invention, especially based on the fact, that in the casting of the mold also the smaller hollow spaces are filled with the metal melt. In another embodiment of the present invention, various devices for capturing the capacity of a fluid metal can be provided in a single dosing oven. Each of these devices has two probes with an exit opening. If these outlet openings (in relation to a quiescent gauge of the fluid metal) remain side by side in the case of a stirred surface of the fluid metal (for example by the filling process in the dosing furnace), the gaining by a formation of the average value. With this it is possible to avoid to a large extent false measurements in a moving metal gauge. However, it is also possible to arrange the outlet openings one on top of the other, so that a state of filling is allowed within wide limits. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers.

Claims

The invention has been described as described above, it is claimed Coroo property contained in the following reiindicaciones: 1. - Dosing oven with a container to receive fluid metal and a device to capture a gauging of fluid metal in a container, where a probe made as a tube is in communication with a source of gas to cause an output current of a gas from the gas source through the probe and its outlet opening, and a pressure measurement device to capture a state of pressure within the probe in dependence on a back pressure caused by the gauging of the liquid metal characterized in that, the pressure measuring device is constituted as a pressure wave switch for capturing a pressure reaction wave within the probes that occurs when the probe opening is closed by the liquid metal, and emitting a corresponding signal and the probe is fixedly fixed to the wall of an ascending tube placed in the container.
2. - Dosing furnace according to the re-viixiation i, characterized in that the probe and / or the riser tube consist of ceramic or essentially ceramic.
3. - Dosing oven according to claim 2, characterized in that the probe is inserted under pressure and / or adhered in a hole.
4. > Dosage oven according to claim 2-3, characterized in that the outlet opening of the probe and / or the perforation have an internal diameter of less than 5mm, preferably less than 2 ram.
5. - Dosing oven according to one of the preceding claims, characterized in that, the pressure wave switch is adjustable in the pressure sensitivity. 6- Dosing oven according to one of the preceding claims, characterized in that a first and a second device are provided for capturing a gauging of fluid metal, which have a first and a second probe with a first and a second opening departure. 7. - Dosing furnace according to claim 6, characterized in that the first exit opening is in relation to a standing capacity of the fluid metal on or to one side of the second exit opening.