DEVICE FOR MEASURING DIMENSIONS OF AN INGOT MOULD

Abstract: Device for measuring the inside dimensions of a cast iron mould. According to the invention a measuring means (11) is movably arranged inside the cast iron mould (10) on one or several guide rails (11), said measuring means comprising a rim with plates, each of which forming a capacitor together with an adjacent portion of the mould wall, and an electronic unit for generating and subsequently processing signals corresponding to the capacitances of the separate capacitors.

Description: Device for measuring dimensions of an ingot mould This invention relates to a device for measuring the in¬ side dimensions of a cast iron mould according to the preamble of the appended claim 1. A cast iron mould in a continuous casting plant is often subjected to relatively strict tolerance demands in re¬ spect of its inside dimensions. A typical embodiment of a cast iron mould is a relatively long curved tube of a square or rectangular cross section. Methods so far known for measuring cast iron moulds utilizing mechanical measuring instruments have the dis¬ advantage that they are relatively slow and that they do not always make possible a reliable measurement of the cast iron mould when it i3 mounted in the continuous casting plant. It is the object of the invention to provide a measuring device for cast iron * moulds making possible a quick measurement when the mould is -mounted in a continuous casting plant and which device may also be used in a workshop for cast iron moulds for adjustment and control. The above-mentioned object is achieved by the device of the invention being provided with the characteristic features indicated in claim 1. According to the invention a measuring means is arranged movable within the cast iron mould on one or more guide rails, said measuring means comprising a rim with plates, each of which forming a capacitor together with an adjacent portion of the mould wall, and an electronic unit for generating and subsequently processing signals corresponding to the capacitances of the separate capa¬ citors. The capacitors formed with the mould wall are preferably connected in oscillating circuits and the signals corre¬ sponding to the capacitances of the separate capacitors can be derived from the frequencies of the oscillating circuits. For measuring a cast iron mould of a " rectangular or square cross section the measuring means *'" according to the invent¬ ion for each mould wall is preferably provided with a num¬ ber of plates disposed beside each other parallel to the wall, opposite plates in the rim being connected in pairs in an oscillating circuit. An illustrative example of the invention will be described more in detail in the following with reference to the en¬ closed drawing where Fig. 1 shows a cast iron mould with a mounted measuring device according to the invention and Fig. 2 shows a section A-A through a mould and the measur¬ ing device according to Fig. 1. The cast iron mould 10 in Fig. 1 consists e.g. of a 700 mm long tube of a square or rectangular cross section. The tube has the same radius of curvature as the continuous casting path, e.g. 6 m. When measuring a guide rail 11 of • he same curvature as the cast iron mould is mounted in the cast iron mould 10, which guide rail is secured at both ends so that it follows the centre line of the cast iron mould. On the guide rail 11 a ' movable slide with a measuring means 12 is arranged, which consists of a rim with plates for capacitive measurement of the inside dimensions of the cast iron mould and an electronic unit for supplying voltage to the measuring means and for processing the signals obtained from the capacitive measurement. It is evident from Fig. 2 showing a section A-A through the cast iron mould 10 and the rim with plates of the measuring means 12, that the measuring means for each mould wall is provided with a number of plates arranged beside each other parallel to the wall. The rim according to Fig. 2 comprises in all 16 plates 1a to 8a and 1b to 8b which are distributed over the four walls of the mould in a way as is apparent from the drawing. The plates are arranged at a relatively short distance from the mould wall, preferably about 2 to 3 mm. As ' the capacitance of the capacitor formed by one plate ' and the adjacent portion of the mould wall is a function of this distance the dimensions of the mould can be obtained from a capacitance measurement. By connecting the separate capacitors formed with the mould walls in oscillating circuits the capa¬ citance measurement can be performed via a frequency mea¬ surement. If opposite plates are connected in pairs a minor eccentricity of the guide rail will not influence the measurement ' result. For the sake of clarity, in Fig. 2 only one oscillating circuit is indicated by means of an oscillator coil 13 having the inductance L, connected to the plates 1a and 1b. Such an oscillating circuit is an oscillator of Colpitt type, the capacitance C of which is obtained as C - ι/c a * 1 T7C, where C is the capacitance between the plate 1a and the adjacent portion of the mould wall and C, is the capacitance between the plate 1b and the adjacent portion of the mould wall. Assuming that the plates 1a and 1b have the same plate area A and at a certain measuring point have the distance d and d, , respectively, from the adjacent mould wall, the above relation can be written as where € and £ Q are dielectric constants. The resonance frequency f of the Oscillating circuit is thus determined by where k is a constant Variations in frequency when the measuring means 12 is moved through the cast iron mould 10, thus correspond to the variations of the inside dimensions of the mould. In the present illustrative example, where 16 plates 1a to 8a and lb to 8b are connected in pairs via an oscillator coil to eight oscillators of Colpitt type, 16 measuring points per mould cross section are obtained, which is enough for measuring a big mould. Measurements can then e.g. be performed at a vertical distance of 25 to 30 mm, which gives about.30 measuring sections for a mould of 700 mm length. The electronic unit which consists of conventional signal processing circuits is not shown in detail in the drawing. The signal from each oscillator can be supplied to a separate counter via a gate- This gate can be enabled by means of a signal from an optically or electronically readable marking on the guide rail and be kept enabled for a predetermined time during which the counter is advanced stepwise. When the gate has been disabled the contents of the counter is transferred to a storage and the counter is reset. It is also possible to utilize only one single counter in the electronic unit and connect the various- oscillat¬ ors to this counter one at a time. After taking the measuring device out of the cast iron- mould the electronic unit can be connected to a printer or a display unit where the contents of the storage is displayed after the necessary calculation to an absolute measure or a deviation from nominal measures. The storage can be made large enough to store data from several cast iron moulds. The measurement result can also be fed directly from the electronic unit to a printer or a display unit. The electronic unit can be battery-operated, which eliminates the need of a cable to the movable measuring means.

Claims: WHAT WE CLAIM IS: 1. A device for measuring the inside dimensions of a cast iron mould comprising at least one guide rail mounted in the cast iron mould and having approximately the same curvature as the cast iron mould, c h a r a c¬ t e r i z e d in that the guide rail is secured at both ends so that it follows substantially the centre line of the cast iron mould, and that a measuring means is arrang¬ ed to run freely on the guide rail, said measuring means comprising a rim with plates, each of which forming a capacitor together with an adjacent portion of the mould wall, said capacitors being connected in oscillating circuits, and further comprising an electronic un t for generating and subsequently processing signals correspond¬ ing to the capacitances of the separate capacitors, said signals being derived from the frequencies of the oscil¬ lating circuits. 2. The device of claim 1 for measuring a cast iron mould of a rectangular or square cross section, c h a r a c t e r i z e d in that the measuring means for each mould wall is provided with a number of plates arranged beside each other parallel to the wall, and that opposite plates on the rim are connected in pairs in an oscillating circuit. 3. The device of claim 1 or 2, c h a r a c t e r ¬ i z e d in that the electronic unit comprises a counter, which is successively advanced stepwise by each one of the different oscillating circuits and the contents of which is transferred to a storage in the electronic unit after each complete forward advancement caused by an oscillating circuit. 4. The device of claim 2, c h a r a c t e r i z e d in that the electronic unit comprises a counter and a gate element for each pair of plates, each counter being ad¬ vanced stepv/ise by the associated oscillating circuit when the respective gate element is enabled by means of a signal from an optically or electronically readable marking on the guide rail.

Inventors: BRUCE I, GARPENDAHL G, LUNDMARK E
Applicants: VIAK AB
Application year: 1980
Main classification: G01B7
IPC codes: B22D11, G01B7