Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D39/00—Equipment for supplying molten metal in rations
  • B22D39/06—Equipment for supplying molten metal in rations having means for controlling the amount of molten metal by controlling the pressure above the molten metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D2/00—Arrangement of indicating or measuring devices, e.g. for temperature or viscosity of the fused mass
  • B22D2/003—Arrangement of indicating or measuring devices, e.g. for temperature or viscosity of the fused mass for the level of the molten metal

Definitions

• the invention relates to a dosing furnace with a vessel for holding liquid metal and a device for detecting a level of liquid metal in a vessel.
• the height of the metal column rising in the dosing tube must be determined, since the dosing quantity is calculated depending on this determination. It is also possible, depending on the detection of the height of the metal column, taking into account other parameters, for example different pressures, to determine the height of the liquid level in the furnace.
• a sensor arrangement for metering furnaces is known from US Pat. No. 4,220,319, in which the sensor consists of a metal needle standing perpendicular or almost perpendicular to the metal surface, which emits a signal when it contacts the liquid metal surface. To wear To reduce the sensor arrangement, the metal needle is pivoted away from the metal surface by an automated mechanical system upon contact.
• Position of the outlet edge determined. Due to the large manufacturing tolerances in the refractory area, the installation of a new metering tube and a new seal etc. can shift the outlet edge by up to 10 mm at a vertical height. In the case of dosing furnaces, a shift in the scanning position in relation to the outlet edge by means of the above-mentioned measures of, for example, 5 mm causes a change in the metal weight metered out of typically 4%. A dosing accuracy of 1 to 2% is required.
• the needle is not readjusted in practice, but rather the pressure or time parameters of the dosage or, in our case, the dosage weight, which is known to be based on the integral method (pressure over time) is determined, changed in order to compensate for the falsification of the dosing weight.
• This has the disadvantage that founders who have stored the metering parameters of different cast parts have to make corrections to these stored values again and again, since the sampling ratios and thus the metering do not remain constant.
• Another disadvantage of the metal needle shown above is due to the principle (because of the required contact with molten metal).
• a layer that forms on the surface of the molten metal after a very short time, such as non-conductive aluminum oxide, must first be broken through by the needle.
• the metal surface bulges downwards as a result of the pressure of the needle.
• this causes an inaccurate measurement result (the needle emits its signal in a position that is too low after the breakthrough, i.e. less metal melt is displayed than is actually present).
• a sensor arrangement for detecting the level of liquid metal is also known, in which the sensor consists of electrically conductive ceramic and is inserted flush in the wall of the vessel or a riser pipe.
• the invention has for its object to provide a dosing furnace with a vessel for holding liquid metal and a device for detecting a level of liquid metal in a vessel, the device detecting the level with good accuracy and being simple and inexpensive in construction and the possibility of deposits of metal (oxide) residues on the sensor is minimized or falsification of the measurement result by deposits is prevented.
• a probe designed as a tube is connected to a gas source for the outflow of a gas of predetermined pressure from the gas source through the probe and out of its outlet opening, the probe being in a fixed spatial association with the vessel such that different levels of the
• a simple device for detecting the level of liquid metal is available for liquid metal, pressures within the probe that can be detected by a pressure measuring device, and a signal for detecting a certain level of liquid metal can be output by the pressure measuring device at a certain pressure threshold value posed that is inexpensive and still records the level with good certainty.
• the tube or the probe can be firmly inserted into the wall or the riser of a dosing furnace, the desired signal being emitted when the liquid level passes the riser.
• the probe is preferably made of ceramic, which means that the possibility of metal deposits on the probe is minimized (particularly in the case of the ceramic / aluminum material pairing). Should thin deposits nevertheless occur (for example due to the roughness of the probe), this does not impair the function of the probe according to the invention, whereas in the case of measuring systems which are based on electrical contacting, even thin deposits can cause a complete failure.
• the ceramic-made probe with an inner diameter of less than 2 mm. Due to the surface tensions that occur, for example of liquid aluminum on the ceramic, the probe does not remain closed by liquid aluminum (even if there is no gas flow).
• the pressure measuring device has a pressure wave switch that is adjustable in pressure sensitivity for measuring a pressure response wave of the gas flowing out of the probe.
• the pressure response wave which occurs when the probe is reached (or closed) by a mirror of liquid metal, is used, for example, as a signal for closing a feed valve in the metering furnace.
• the adjustability of the pressure wave switch enables simple adjustment to the conditions of the respective installation location, which is also possible during operation.
• the dosing oven has several devices for detecting a Contains levels of liquid metal, each having a probe with an outlet opening. If these outlet openings lie next to each other (with respect to a stationary level of the liquid metal), in the case of a moving surface of the liquid metal the level can be determined by suitable averaging of the pressures measured in the probes .
• Fig. 1 shows schematically a section through a
• Fig. 2 is an enlarged partial view of the end of the tubular probe inserted into the riser wall.
• a dosing furnace 1 with a vessel 12 in which liquid metal, for example aluminum, is received in a bath 2.
• a riser pipe 3 is inserted, which is guided through the wall 4 of the metering furnace 1 to the outside.
• Liquid metal is metered out via the riser pipe 3. This can be done (according to a sensor device) by regulated pressurization in the interior of the vessel 12 in order to pass liquid metal through the
• the discharge pipe 13 fills the molten metal, preferably aluminum, for example into molds provided therefor. It is important that the amount of molten metal driven out of the vessel 12 onto the Volume of the molds is matched. For metering out, it is necessary that the height of the metal column in the metering furnace (or in the riser pipe 3) is recorded exactly, a pneumatic sensor device 6 being used for this recording.
• the pneumatic sensor device has a probe 5 designed as a tube, which is preferably made of ceramic, and which is inserted into the wall 7 of the riser tube 3 according to FIG. 2.
• a bore 8 designed as a stepped bore is provided in the wall 7, the end of the probe 5 being pressed and / or glued into the riser wall 7 from the outside in the bore part with a larger diameter, and the smaller diameter of the stepped bore 8 corresponds approximately to the inner diameter of the tube 5.
• the probe 5 is connected to a gas source 10 via a pressure measuring device 9.
• the gas source supplies gas at a certain pressure to the probe 5, which flows out of its front end and through the bore 8.
• the flow conditions at the end of the probe change and a change in pressure occurs in the probe.
• This pressure change is determined by the pressure measuring device 9. It is therefore an indirect method for measuring the level, since the level does not have to be carried out directly (for example by touching a contact element provided for this purpose). Instead, the influence of a metal level to be measured on given flow conditions (a gas that flows out of a gas source with a defined pressure) is determined. This influence can be determined via a change in pressure of the outflowing gas in the probe 5. Are about this pressure change So statements about the level of the liquid metal are possible. A particularly clearly measurable change in pressure occurs when the open end of the probe 5 (or the bore 8) is closed by the liquid metal.
• the pressure curve is measured before the actual measurements as the level approaches or rises and a pressure threshold value is determined at which the level has a predetermined assignment to the end of the probe 5.
• the pressure measuring device 9 then sends a corresponding signal at its output 11 to the further evaluation control devices.
• any measuring device for measuring the pressure in the tube 5 is suitable as the pressure measuring device 9.
• a bridge circuit can be used in which two chokes have a fixed cross section in
• the output of the first throttle is connected to a throttle of variable cross-section and the output of the second throttle to probe 5. Between the outputs of the first and second throttles of fixed cross-section there is a volumetric flask which changes in position due to pressure fluctuations.
• the measuring device can be adjusted so that the pressure is essentially present on both sides of the measuring piston. If the flow conditions at the tip of the probe 5, that is to say at the bore 8, changes due to the advancement or passing of the metal mirror, the position of the measuring piston changes, thereby making a statement about the pressure present can be.
• the position of the volumetric flask can be detected, for example, via a reed contact.
• a so-called pressure wave switch is used, the setting range of which is approximately between 0.5 and 5 mbar.
• These switches have a membrane on the inside, on which a contact is attached. One side of the membrane is connected to the ambient pressure, the other side is connected to the sampling tube or probe 5. If the sampling tube 5 is now closed with a liquid, the pressure in the sampling tube 5 and thus on one side of the membrane increases and this is pressed against a fixed contact, so that the contact on the membrane comes into contact with the fixed one. This allows current to flow when the pressure response threshold is reached.
• the adjustment of the pressure sensitivity is done simply by adjusting the distance of the fixed 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 contact is more or less far from the membrane contact, so that more or less pressure must be applied to bring both contacts into contact.
• Inner diameter of the probe 5 or the bore of less than 2 mm and a suitable material pairing (ceramic for the parts of the probe 5 which come into contact with the molten metal and the component containing the bore 8, in this case the riser tube 3) a closure made difficult by molten metal. Because of the surface tensions that occur with certain material pairings, for example between the ceramic and liquid aluminum, a closure is even ruled out here. This is of crucial importance for the present invention, especially when considering the fact that, for example in the form of casting, even the smallest voids are filled with molten metal.
• Dosing furnace can be provided.
• Each of these devices has its own probe with an outlet opening. If these outlet openings lie next to one another (with respect to a stationary level of the liquid metal), in the case of a moving one
• the level can be determined by suitable averaging. This means that possible incorrect measurements due to a moving metal level are largely ruled out.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
• Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
• Noodles (AREA)
• Valve-Gear Or Valve Arrangements (AREA)
• Commercial Cooking Devices (AREA)
• Peptides Or Proteins (AREA)
• Vending Machines For Individual Products (AREA)
• Medicines Containing Plant Substances (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1996
  • 1996-11-11 DE DE19647713A patent/DE19647713C2/de not_active Expired - Lifetime
• 1997
  • 1997-11-10 JP JP52205298A patent/JP4327908B2/ja not_active Expired - Lifetime
  • 1997-11-10 BR BR9713002-8A patent/BR9713002A/pt not_active IP Right Cessation
  • 1997-11-10 US US09/297,992 patent/US6303073B1/en not_active Expired - Lifetime
  • 1997-11-10 AT AT97951076T patent/ATE243580T1/de not_active IP Right Cessation
  • 1997-11-10 EP EP97951076A patent/EP0946314B1/fr not_active Expired - Lifetime
  • 1997-11-10 DE DE59710352T patent/DE59710352D1/de not_active Expired - Lifetime
  • 1997-11-10 CA CA002271207A patent/CA2271207C/fr not_active Expired - Fee Related
  • 1997-11-10 ES ES97951076T patent/ES2201336T3/es not_active Expired - Lifetime
  • 1997-11-10 WO PCT/DE1997/002663 patent/WO1998020996A1/fr not_active Ceased

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