JPH0244927Y2 - - Google Patents

Description

[Detailed description of the invention] 1. Industrial application field This invention can be used to heat and melt various casting materials using heating means such as high-frequency induction heating and arc discharge to produce small-sized products such as dentures, dental repairs, and decorative items. The present invention relates to a precision casting apparatus that uses a self-scanning image detector to determine casting timing for casting precision casting products.

2. Prior Art Conventionally, in precision casting equipment, the timing for pouring molten metal into a mold (hereinafter referred to as casting timing) has generally been determined visually by an operator; (hereinafter referred to as casting temperature) is generally slightly higher than the melting point of the material, and its temperature range is extremely narrow, and even if it exceeds or falls below that temperature range, the cast product will be defective. Therefore, determining the casting timing is an extremely important element during the casting process, and even highly trained people often make mistakes when visually judging the timing, resulting in low product yields. This loss is a major problem, especially in dental applications that use expensive alloy materials. As a means to solve this problem and determine the optimal casting timing practically and accurately, the authors devised three inventions that have already been filed.
-227962) Precision casting device" (hereinafter referred to as invention (A)), "Patent application No. 1983-102325, Japanese Patent Application No. 1983-244458
No.) Precision casting method and device” (hereinafter referred to as invention (B)), “Patent Application No. 115071, 1983-
No. 257962 "Brightness Distribution Photography Type Precision Casting Apparatus" (hereinafter referred to as invention (C)). Devices based on a series of these inventions have developed rapidly in recent years as image detectors, are widely used in television cameras, etc., and are generally CCD
(Charge Coupled Device)
It is used as a sensor. This CCD image
As is well known, a sensor is also called a self-scanning imaging device because it is configured to convert light into a signal charge and perform photosensitive storage and transfer. Therefore, in this invention, the above-mentioned one-dimensional or two-dimensional CCD image sensor is collectively expressed as a self-scanning image detector, and in the specification, it is abbreviated as image sensor for simplicity. There is. This image sensor captures the synchrotron radiation image emitted by the casting material in the crucible as a plane image in the case of invention (A), and as a brightness distribution image in the cases of inventions (B) and (C). The casting timing is determined based on the point at which the contour shape of the image changes, or in the latter case, the point at which the top of the distribution image becomes straight. The device of invention (B) above performs visual judgment using a video display, but the devices of inventions (A) and (C) do not require a video display and process image signals to automatically perform casting. It is configured so that it can be done. The above-mentioned image sensor has excellent light detection ability over a wide wavelength range from the visible light region to the infrared region of about 1000 nm, and is capable of self-scanning, so that the viewing window in the melting chamber will not be fogged by gases or metal vapor generated during melting. Changes in the shape and brightness distribution of the material inside the crucible are captured moment by moment, and changes in the contour shape or the point at which the top of the brightness distribution image becomes flat can be easily captured using either images or signals. Therefore, the entire casting process is automated without any training required, and the long-standing problems of the precision casting industry are solved at once. Since a focusing lens system is used as an imaging means for the fused material radiation, the brightness of the fused material imaging light is too high and exceeds the light receiving capacity of the image sensor, resulting in a phenomenon in which the image is distorted (generally referred to as blooming). occurs. Therefore, it is necessary to use a filter that appropriately attenuates the amount of light. Furthermore, among the various aberrations that the lens has, the ones that are particularly problematic in the above device are image curvature and distortion, and as is well known, the former causes the center of a horizontal plane image of an object to curve toward the distance, and the periphery to curve toward the near side. Since the image is captured at a minimum, if you focus on the center, the edges will be blurred, and if you focus on the edges, the center will be blurred. The latter cannot accurately and clearly image the shape of the object inside the crucible, for example, it images a square object into a square, pointed shape like a spool. For this reason, the condensing lens system of the above device uses glass with special optical properties.
In addition, several lenses are combined to correct the curvature and distortion of the image and reduce residual aberrations to a point where they can be ignored in practical terms. Concentrating lens systems made in this way are not only complex and expensive, but also have a shallow depth of focus, which means that the surface height of the material in the crucible changes as melting progresses. Therefore, there is a problem that the sharpness of the image of the image sensor is reduced.

3. Purpose This invention solves the problem of the focusing lens system of precision casting equipment using the image sensor mentioned above, and allows the high-intensity emitted light from the molten material in the crucible to be transmitted at a brightness suitable for the image sensor without the need for a neutral density filter. Since there is no lens, there is no aberration such as curvature or distortion of the image, and the feature is that it is always in focus at any distance, so the synchrotron radiation image of the molten material in the crucible is always clearly imaged. We will provide an inexpensive precision casting device with a simple structure that can produce high-quality cast products with high efficiency by providing an imaging system based on the principle of a pinhole camera that focuses an image on a sensor, determining the optimal casting timing, and producing high-quality cast products with high efficiency. That is.

4. Structure This invention is a method for heating and melting a small amount of casting material in a crucible using a heating means such as a high-frequency induction heating device, and determining the casting timing for pouring this molten metal into a mold. The imaging system of the apparatus is configured as follows, in which the progress state of melting is imaged by an image sensor and the image signal is used. That is, for example, a cylindrical dark box is formed in the optical path of the emitted light of the molten material in the crucible, a pinhole is provided at the optical axis position of one end surface of the dark box perpendicular to the optical path axis, and other dark boxes opposite to this pinhole are provided. A pinhole with the image sensor installed in the center of the end. This apparatus uses a camera-type imaging system to always clearly form a radiation image of the molten material in the crucible on the light receiving surface of the image sensor in a similar or the same shape.

5 Examples Examples of this invention will be described below with reference to the drawings. FIG. 1 is an external perspective view of an embodiment of a precision casting apparatus in which the heating means is of a high-frequency induction heating type. Device 1
The bottom outer surface part 2 of the heating chamber, the vertically movable casing 3 containing the mold holder therein, and the lower chamber upper surface part 4 are exposed to the outside, and the other parts are packaged with upper and lower casings 5 and 6. are doing. The device according to the first embodiment of this invention is according to the above-mentioned invention (B), and a video display device such as a display CRT 8 is always provided on the operation panel 7, but the device according to the second and third embodiments of this invention is That is, in the apparatuses according to inventions (A) and (C), the casting timing is determined by the signal processing circuit, so the video display 8 is not necessarily required. However, some of the second and third devices are additionally provided with an observation window 9 (indicated by a dotted line), which is not used to determine the casting timing, but to occasionally visually observe the situation inside the crucible.
10 on the operation panel is a group of operation push buttons, and 11 is a group of indicator lights, and these are not much different between the first and third embodiments. Next, as shown in FIG. 2, the heating chamber 13 common to the apparatuses of the first to third embodiments is
The configuration of the surroundings and the pinhole camera type imaging system 14, which is the main part of this invention, will be explained. The convex mold 15 has a crucible 16 on its upper protrusion, a precision casting cavity 17 and a runner 18 formed by the lost wax method, and is integrally molded with the crucible 16 inside the refractory cylindrical body 19, i.e. The convex mold base 20 is housed in a heating chamber 13 and supported on a mold pedestal 21 via an asbestos ring 22 . This pedestal 21 is pushed up at a predetermined pressure by, for example, a pneumatic cylinder piston 23 on the central axis of the vertically movable housing 3 shown in FIG.
The shoulder portion of the heating chamber 2 is pressed against the bottom outer surface portion 2 of the heating chamber through an asbestos packing 24. A high-frequency induction coil 25 is wound around the fireproof cylindrical body 19, and a viewing window 26 made of transparent fireproof material is provided to seal the upper end of the heating chamber 13, and an exhaust pipe is provided to reduce the pressure inside the heating chamber 13. 27 and an inert gas introduction/output pipe 28 for pressurizing pouring of molten metal. The configuration around the heating chamber 13 is the same as the conventional device, and the casting material (M) in the crucible 16 is
An image sensor 30 that images the progress of melting.
The main body is also the same as the three devices described above. The difference lies in the configuration of the dark box or pinhole camera type imaging system 14 provided on the emitted light path (RL) of the material (M) in the crucible. The imaging system 14 includes a cylindrical body 31, a light receiving section 33 having a pinhole 32 at one end, and a detecting section 34 forming the other end surface of the dark box.
and a support mechanism 36 that holds them against the heating section frame substrate 35. The cylindrical body 31 has a length sufficient to form an image of the entire molten material (M) in the crucible 16 on the light receiving surface 37 of the image sensor 30, that is, from the pinhole 32 to the sensor light receiving surface. The distance (L ₁ ) corresponds to, for example, 200 mm, and a large-diameter ring body 39 that is rotatably connected to the light receiving section 33 via a bearing 38 is joined to one end (lower end in this example). There is. A U-shaped groove 40 into which a round belt (not shown) fits is cut into the outer peripheral edge of the ring body 39. The light receiving section 33 includes a pinhole setting section 43 that aligns the pinhole 32 with the radiation optical path central axis (RLc) and fixes the pinhole plate 42 so as to be accurately perpendicular to the central axis (RLc), A transparent glass 44 holds the pinhole 38 and prevents dust from adhering to the pinhole 32.
The protective window 45 formed by
It is installed at an inclination angle of 45°. A transparent material is used for the protective window 45 in the first embodiment device that uses the video display 8 and in the second and third devices that do not have the observation window 9 shown in FIG. 1. . When the observation window 9 is provided, the protective window 45 is made of, for example, a brown smoke colored acrylic resin material 44'.
is inserted, and part of the emitted light is dispersed in the direction of the dotted arrow (a). For simplicity, the diagram omits the refraction of light by the glass 44. Next, a pinhole object distance adjustment mechanism 41, which is a specific example of a pinhole object distance adjustment means, which is one of the essential parts of this invention, will be explained. A pair of upper and lower arms 47, 47' installed on the light-receiving unit base 46 are attached to the same 1
The upper arm 47 is slidably mounted on the pair of support columns 48, and the upper arm 47 rotatably engages the tip of a threaded rod 49. The threaded rod 49 is screwed into a horizontal beam 50 constructed above the pair of supports 48 of the support mechanism 36. With this configuration, by rotating the threaded rod 49, the light receiving portion 33, that is, the pinhole 3
By slightly moving the position 2 in the direction of arrow (b), it is possible to adjust and set the objective distance (L ₂ ) that optimizes the size of the light image on the light receiving surface 37 described above. Next, the detection unit 34 forms a sealed container with a cover 54 and a base plate 53 assembled on a flange plate 52 connected to the other end (in this example, the upper end) of the cylindrical body 31 by welding or the like. . The above-mentioned image sensor 30 is attached to a plate A56 protruding from a support A55 installed on the base plate 53, and the support B
On the plate B58 of 57, a video signal generation circuit 59 is mounted in the first embodiment, and signal processing circuits 60 and 61 are mounted in the second and third embodiments, respectively. The above is the configuration of the pinhole camera type imaging system 14. In this configuration, by making the diameter of the pinhole 32 as small as possible, it is possible to form an image with excellent resolution. High-brightness synchrotron radiation is attenuated and image
The sensor does not exhibit blooming. Furthermore, although the length (l) of the light receiving surface 37 of the image sensor 30 is short (for example, 30 mm),
Since it has up to 2,600 photosensitive pixels, the melting state of the material (M) in the crucible 16 is captured moment by moment with extremely high resolution. In addition, even if the distance (L ₂ ) from the pinhole 32 increases due to changes in the shape of the material (M) as the melting progresses, the focus will always be on the sensor light receiving surface, and there will be no slight change in image sharpness. Does not occur. Next, with reference to FIG. 3, the circuit configuration of the device according to the first embodiment of this invention and its image will be described. The details are shown in the specification of invention (B), so they will be briefly explained here. The image sensor 30 is one-dimensional (line imaging type)
Or a two-dimensional (area imaging type) sensor may be used, but usually a one-dimensional sensor is used, and the imaging system 14 shown in FIG.
uses a fixed imaging system 14' (not shown) which does not require a bearing 38 and has a simple ring body 39.
In the figure, the signal (D ₁ ) of the sensor 30 is the luminance distribution (I・B) on the center line of the material (M), for example.
signal, and the video signal generation circuit 5 in the detection unit 34
9, the signal is converted into a luminance distribution video signal (D ₂ ) and input to the video display 8. The figure shows an image of the display 8, where the horizontal axis (P) indicates the position of the crucible 16 in, for example, the X direction (direction along the plane of the paper in FIG. 2), and (d) corresponds to the inner diameter of the crucible 16. The vertical axis (B) indicates the brightness of the material (M). In the figure, (t ₁ ) to (t ₄ ) of the brightness distribution image (I・B) show changes in time series as the heating progresses.
The point at which the top becomes almost flat as shown in (t ₄ ) is when the material (M) has completely melted and reached the above-mentioned casting temperature. Therefore, the metal is poured after a predetermined mooring time based on this point (t ₄ ).

Next, referring to FIG. 4, a second embodiment of this invention, that is, an apparatus according to invention (A) will be described. Since details similar to those described above are shown in the specification of invention (A), the rotating means of the one-dimensional image sensor 30 will be mainly explained here. Link body 3 joined to cylindrical body 31 explained in FIG.
A rubber belt 65 having a circular cross section, for example, is stretched between the U-shaped groove 40 of 9 and a pulley 64 of a reversible rotary motor 63 fixed to a heating unit frame substrate (not shown) (FIG. 2, 35). The motor 63 is the detection unit 3
The image sensor 30 of the imaging system 14 is intermittently rotated six times by 30 degrees in the direction of the arrow (C), for example, by the CPU 60A of the microcomputer and the rotation control circuit 60B of the signal processing circuit 60 in the signal processing circuit 60 in the six directions. When the imaging is completed, the robot quickly returns to the original position in the opposite direction. The planar image signal (D ₃ ) of the material (M) obtained by this imaging is sent to the CPU 6 above.
A contour image significant difference determination circuit group 60C in the detection unit 34 controlled by 0A, that is, performs signal processing to determine that the contour of the plane image has undergone a predetermined change due to the progress of melting, When this determination signal (S) is output, each of the circuits and devices 66 to 69 shown in the figure is activated, and pouring of metal into the mold is automatically performed. Note that when a two-dimensional sensor is used as the image sensor 30, the imaging system 14 does not require rotation by the motor 63, and may be a fixed imaging system 14' without the bearing 38 described above.

Next, referring to FIG. 5, a third embodiment of the device of this invention, that is, a device according to invention (C) will be described. Since details similar to those described above are shown in the specification of invention (C), the main points will be briefly explained here. Like the first device, this device usually uses a one-dimensional sensor, the imaging system 14 is fixed, and the signal (D ₁ ) of the one-dimensional sensor has a brightness distribution (I・B ) is a signal. The signal processing circuit 61 housed in the detection unit 34 is composed of a CPU 61A and a brightness distribution image encoding and determination circuit group 61B, and is configured to perform brightness distribution (I/B) as shown in FIG.
The image is encoded into a binary signal, and by comparison with a reference binary signal, it is determined whether the top part has been flattened as shown at (t ₄ ) in the figure, and a determination signal (S) is output. be. The circuit/device operated by this signal (S) is the same as the second device, and the figure separately shows the mooring time setter 66A included in the signal generation circuit 66 in the second device. .

The above are three embodiments of this invention, but this invention is not limited to the illustrations and explanations. For example, the radiation light path (RL) on the crucible in FIG.
For example, by installing a reflecting mirror tilted at 45° to change the optical path in the direction of the dotted arrow (a) and installing the imaging system 14 there, or by using several reflecting mirrors together, the direction of the radiation optical path can be changed. In addition, the position of the imaging system can be set freely. Further, the dark box of the imaging system is not limited to a cylindrical shape, but may be a rectangular tube shape. Further, the mechanism 41 of the pinhole objective distance adjusting means is not limited to the one shown in the drawings. In addition, although the explanation was given using a high-frequency induction heating system, if the arc discharge heating system is configured so that the melting state of the material inside the crucible can always be imaged, the casting timing can be adjusted using a pinhole camera type imaging system. You can decide. Therefore, it falls within the scope of this invention.

6 Effects This idea is structured as above, so
This solves the problem of the converging lens system of precision casting equipment, which uses an image sensor to take an image of the casting material in the crucible and determines the casting timing. In other words, it takes advantage of the drawbacks of pinhole cameras, which generally have a large f-number (the reciprocal of the aperture ratio and is also called the aperture number) and takes a long time to expose, to capture high-brightness synchrotron radiation images of melted material in a crucible. image without using a neutral density filter.
The light is attenuated within the light receiving capacity of the sensor, and the image is faithfully formed in response to the ever-changing changes in the light image, and there is no lens aberration such as image curvature or distortion. A pinhole camera-type imaging system that constantly focuses the synchrotron radiation image clearly on the image sensor without being affected by fluctuations in the image sensor, combines this with the image sensor's high resolution and light detectability. The present invention provides a simple, easy-to-manufacture, and inexpensive device that can pour metal at the optimal casting timing and efficiently produce high-quality cast products.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view of a high-frequency melting and pressure precision casting apparatus as an embodiment of this invention, and FIG. 2 is a longitudinal cross-sectional view showing the configuration of the heating section and imaging system of the above-mentioned apparatus.
FIG. 3 is a circuit block diagram of a device according to the first embodiment of this invention, the figure shows a luminance distribution image of the video display screen of the above device, and FIG. 4 is a circuit diagram of a device according to a second embodiment of this invention. Block Diagram FIG. 5 is a circuit block diagram of a third embodiment of the device of this invention. 1... Precision casting device, 8... Image display, 13
... Heating chamber, 15 ... Convex mold, 14 ... Dark box (pinhole camera type imaging system) 16 ... Crucible,
17...Precision mold cavity, (M)...small amount of casting material, (RL)...radiated light optical path of molten material in crucible,
(RLe)...The above radiation path axis, 30...Self-scanning image detector (CCD image sensor), 32...
...Pinhole, 34...Other end surface (detection section) of the above 14, 37...Light receiving surface of the above 30, 41...Pinhole objective distance adjustment mechanism, 42...1 of 14 above
End surface (pinhole plate), 60A, 60B, 61C,
61A, 61B... Image signal processing circuit.

Claims (1)

[Claims for Utility Model Registration] 1. A small amount of casting material contained in a crucible is melted through a heating means, the progress of melting is imaged by a self-scanning image detector, and this image signal is directly converted into an image. In an apparatus for determining the timing of pouring molten metal into a mold by displaying a display or performing signal processing, forming a dark box that surrounds and covers the emitted light path of the molten material in the crucible;
A pinhole is provided at the optical axis position of one end surface of the dark box that is perpendicular to the optical path axis, and the detector is installed in the center of the other end surface of the dark box opposite to this pinhole. A precision casting apparatus, characterized in that a pinhole object distance adjusting means is provided to move and set the position along the optical axis, and an emitted light image of the molten material in the crucible is formed on the light receiving surface of the detector. 2. The precision casting apparatus according to claim 1, wherein the self-scanning image detector is a one-dimensional detector. 3. The precision casting apparatus according to claim 1, wherein the self-scanning image detector is a two-dimensional detector.