EP0904871A1

EP0904871A1 - A mechanism for blowing molding sand in blowing machines

Info

Publication number: EP0904871A1
Application number: EP97116715A
Authority: EP
Inventors: Yoshihura Yamamoto; Tatsumi Fujita
Original assignee: Sintokogio Ltd
Current assignee: Sintokogio Ltd
Priority date: 1996-06-28
Filing date: 1997-09-25
Publication date: 1999-03-31
Also published as: JPH1015644A

Abstract

A molding sand blowing mechanism is provided wherein compressed air blown into the mechanism can pass through the inner cylindrical chamber with little resistance applied thereto, the inner cylinder can be easily manufactured, and whether the model box is adequately filled with molding sand does not depend on the quantity of molding sand in the inner cylindrical tube. The sand blowing mechanism comprises outer and inner cylindrical tubes 5,7, to form exhaust and air supply guiding chambers 11,12, and a plurality of nozzles 19,39 provided in the inner tube 7 for jetting compressed air into the air supply guiding chamber 12 toward the periphery of the inside of the inner tube 7.

Description

Technical Field

This invention relates to an improvement in a mechanism for blowing molding sand in a blowing machine, wherein moisturized molding sand, such as molding sand for a cold-box method and molding sand containing a furan resin, is blown into a model box by using compressed air.

Prior Art

The conventional mechanism for blowing molding sand of this kind comprises an outer cylindrical tube having a hollow chamber therein and holes communicating with the hollow chamber for supplying molding sand and compressed air, respectively, an inner cylindrical tube forming an inner cylindrical chamber therein and having many slits on its body portion, and a ring-form chamber for guiding an air flow, said chamber being disposed between the outer cylindrical tube and inner cylindrical tube and under the compressed air supply hole, thereby causing compressed air to be fed into the air-guiding chamber and then through the slits into the inside of the inner cylindrical chamber so as to fluidize the molding sand within the inner cylindrical chamber, while preventing a so-called shelving phenomenon.
In the thus-structured conventional molding sand blowing mechanism, slits about 0.3mm in width, which is less than the sand particle size, are provided so as to prevent molding sand from being discharged through the slits along with the remaining compressed air when the compressed air remaining in the inner cylindrical chamber is discharged through the slits after molding sand has been blown into the model box. Thus, a significant loss of pressure results when the compressed air passes through the slits in the inner cylindrical chamber. Therefore, it is impossible to provide compressed air having enough of a volume and pressure to fluidize the molding sand in the inner cylindrical chamber when molding sand is fed into the model box by feeding compressed air into the molding sand blowing mechanism. As a result, a problem occurs in that feeding enough molding sand to fill the model box is sometimes impossible.
Problems also occur in that making slits takes lots of labor and time, and it largely depends on the quantity of molding sand fed into the inner cylindrical chamber as to whether the model box is adequately filled with molding sand.
This invention aims to solve the above-mentioned problems. Its purpose is to provide a mechanism for blowing molding sand, wherein the compressed air blown into the mechanism can pass through the inner cylindrical chamber with little resistance to its flow and wherein the inner cylindrical tube can be easily made, and wherein whether the model box is adequately filled with molding sand does not depend on the quantity of the molding sand in the inner cylindrical chamber.

Disclosure of Invention

To achieve the above-mentioned purpose the mechanism of this invention for blowing molding sand is used in a blowing machine for blow-forming molds so as to blow moisturized molding sand into a model box by using compressed air. The molding sand blowing mechanism comprises an outer cylindrical tube extending vertically, an inner cylindrical tube disposed inside the outer cylindrical tube to form an annular space therebetween, an exhaust guiding chamber, and an air-supply guiding chamber provided respectively in an upper and lower relationship in the space, formed by dividing the space with a partition member, ventholes disposed in the upper portion of the inner cylindrical tube and communicating with the exhaust guiding chamber, an exhaust port disposed in the outer cylindrical tube and communicating with the exhaust guiding chamber, an air supply hole disposed in the outer cylindrical tube and communicating with the air-supply guiding chamber, and a plurality of nozzles disposed at the lower part of the inner cylindrical tube for jetting compressed air in the air-supply guiding chamber toward the periphery of the inside of the inner cylindrical tube, thereby agitating and fluidizing the molding sand in the inner cylindrical chamber by the compressed air jetted from the nozzles.

Brief Description of Drawings

Fig. 1 is a front view, partly in section, of a molding sand blowing mechanism of this invention in a blowing machine.
Fig. 2 is an enlarged front view, partly in section, of a first embodiment of an inner cylindrical tube of this invention.
Fig. 3 is a section of Fig. 2 cut along the line A - A.
Fig. 4 is an enlarged front view, partly in section, of a second embodiment of an inner cylindrical tube of this invention.
Fig. 5 is a section of Fig. 4 cut along the line B - B.

Modes for Carrying Out the Invention

We will now explain the embodiments of this invention in detail by reference to Figs. 1 - 5. As is shown in Fig. 1, a mechanism 1 for blowing molding sand is mounted on a traveling car (not shown) via a resilient supporting member such as coil springs so that the mechanism 1 is supported resiliently and movably in a vertical direction. The mechanism 1 comprises an outer cylindrical tube 5 and an inner cylindrical tube 7 disposed inside the outer cylindrical tube 5 and having a flange 6, through which the inner tube 7 is detachably mounted therein. The space inside the inner cylindrical tube 7 constitutes an inner cylindrical chamber 37. On an upper portion of the inner cylindrical chamber 37 is provided a through hole 3 of a given size, through which hole molding sand is fed into the chamber 37.
An annular space 8 is formed between the outer cylindrical tube 5 and the inner cylindrical tube 7. This annular space 8 is divided into an exhaust-guiding chamber 11 and an air supply guiding chamber 12. The exhaust guiding chamber 11 is positioned above the air supply guiding chamber 12, by means of both a partition member 9 fixed to an outer upper portion of the inner cylindrical tube 7 and a sealing member 10 mounted on the outer end of the partition member 9. The bottom portion of the outer cylindrical tube 5 is widened, with a proportionatly widened space therein, and in section has a rectangular shape. On the bottom surface of the outer cylindrical tube 5 is mounted a blow plate 21 having a plurality of holes 20 for jetting molding sand therethrough.
A lower additional outer cylindrical tube 2 and an upper additional outer cylindrical tube 4 having the same diameter as the upper portion of the lower additional outer cylindrical tube 2 are provided on the outer periphery of the upper end of the outer cylindrical tube 5. Both additional outer cylindrical tubes serve as a part of the outer cylindrical tube 5 for providing a compressed air-supply path to the inner cylindrical chamber 37 via the air supply guiding chamber 12. The two additional outer cylindrical tubes 2 and 4 are airtightly connected to form one body. The lower part of the lower additional outer cylindrical tube 2 converges in the downward direction at the outer cylindrical tube 5.
As shown in Fig. 2, a plurality of ventholes 13, communicating with the exhaust guiding chamber 11, is formed in the upper part of the inner cylindrical tube 7, and wire netting 14, through which molding sand cannot pass, is wound around the outside of the area where the ventholes 13 are provided in the upper outer surface of the inner tube 7 to cover the holes 13.
As shown in Figs. 2 and 3, a plurality of nozzles 19 are arranged in the lower part of the inner cylindrical tube 7. Each of these nozzles 19 extends inwardly from the inner surface of the inner cylindrical tube 7 and each nozzle tip is horizontally bent as shown by an arrow in Fig. 3 so that it can jet compressed air in the air supply guiding chamber 12 toward the periphery of the inner surface of the inner cylindrical tube 7. As shown in Fig. 1, an exhaust port 15, communicating with the exhaust guiding chamber 11, is provided in the upper outer cylindrical tube 4. The exhaust port 15 is provided with a valve 17 and a communicating tube 16 that connects the exhaust port 15 and the valve 17. An air supply hole 18, communicating with the air supply guiding chamber 12, is provided on the upper surface of the upper additional outer cylindrical tube 4.
A compressed air supply mechanism 22 is fixed above the outer and inner cylindrical tubes 5,7. The compressed air supply mechanism 22 comprises a tank 23 for storing compressed air, a box-shaped body 25 connected to the tank 23 via a communicating tube 24, a valve 27 for opening and closing a communicating hole 26 of the body 25, and a cylinder 28 containing a piston (not shown) for moving the valve 27 up and down. Compressed air stored in the tank 23 is supplied to the air supply hole 18 provided in the upper additional outer cylindrical tube 4 via the body 25 when the valve 27 is moved up.
In the thus-constituted apparatus (Fig. 1), the outer and inner cylindrical tubes 5, 7 are moved up along with a model box (not shown) by means of elevating means (not shown) so as to make the upper surface of the outer cylindrical tube 5 abut the bottom surface of the body 25 of the compressed air supply mechanism 22, after molding sand S of a required amount has been fed into the inner cylindrical chamber 37 from the through hole 3 of the molding sand blowing mechanism 1. After the valve 17 is closed, compressed air in the tank 23 is supplied to the air supply hole 18 via the body 25 by contracting the piston in the cylinder 28 to move the valve 27 up so as to open the communicating hole 26.
The supplied compressed air passes through the air supply guiding chamber 12, and then it is jetted from nozzles 19 toward the periphery of the inner surface of the inner cylindrical tube 7, thereby the molding sand S in the inner cylindrical chamber 37 being jetted from sand jetting holes 20 to be blown into the model box after the sand S has been fluidized so as to whirl around in the direction of the arrow of Fig. 3. Since all the molding sand S in the inner cylindrical chamber 37 is fluidized by means of nozzles 19 disposed in the lower part of the inner cylindrical tube 7, whether the model box is adequately filled with molding sand does not depend on the quantity of the molding sand contained in the inner cylindrical chamber 37. The valve 27 is closed by expanding the piston in the cylinder 28 to close the through hole 26, and then the valve 17 is opened, after molding sand S has been blown into the model box. Thus, the compressed air remaining in the outer and inner cylindrical tubes 5,7 is discharged from the valve 17 after passing through the air supply holes 13, the exhaust guiding chamber 11, and the exhaust port 15.
In the above-mentioned embodiment the nozzles 19 are disposed in the inside of the inner cylindrical tube 7. However, as shown in Figs. 4 and 5, many nozzles 39 constituted by tubes can be mounted on the outer surface of the lower part of the inner cylindrical tube 7 such that the tubes slant at a given angle toward the outer surface, the holes of which nozzles open to the inner cylindrical tube 7 without protruding into it. This structure has an effect in that the inner surface of the inner tube can easily be cleaned. Also, in the above-mentioned embodiment the ventholes 13 and wire netting 14 of the inner cylindrical tube 7 may be replaced by many slits about 0.3mm in diameter, if the slits function like the wire net.
As is clear from the above explanation, the thus-structured molding sand blowing mechanism of this invention has excellent effects in that the compressed air blown into the mechanism can pass through the inner cylindrical tube with little resistance to its flow, since the slits are replaced by nozzles with a much greater aperture, the inner cylindrical tube can be easily manufactured, and whether the model box is adequately filled with molding sand does not depend on the quantity of the molding sand in the inner cylindrical tube.

Claims

A mechanism for blowing molding sand in a blowing machine, wherein moisturized molding sand is blown into a model box by using compressed air, the mechanism comprising an outer cylindrical tube extending in a vertical direction, an inner cylindrical tube disposed inside the outer cylindrical tube to form an annular space therebetween, an exhaust guiding chamber, and an air supply guiding chamber provided respectively in an upper and lower relationship in the space, formed by dividing the space by a partition member, ventholes communicating with the exhaust guiding chamber and disposed in the upper portion of the inner cylindrical tube, an exhaust port communicating with the exhaust guiding chamber and disposed in the outer cylindrical tube, an air supply hole, communicating with the air supply guiding chamber and disposed within the spece between the outer cylindrical tube and the inner cylindrical tube, and a plurality of nozzles disposed at the lower part of the inner cylindrical tube for jetting compressed air in the air supply guiding chamber toward the periphery of the inside of the inner cylindrical tube.
A mechanism of claim 1, wherein each of the nozzles extends inwardly from the inner surface of the inner cylindrical tube and the nozzle tip is bent horizontally.
A mechanism of claim 1, wherein each of the nozzles is a tube mounted on the outer surface of the inner cylindrical tube such that each tube slants at a given angle toward the outer surface, the hole of each of which tube is open to the inner cylindrical tube.