GB2079654A - Moulding method and apparatus - Google Patents

Abstract

A moulding method and a moulding apparatus in which a cover member 9 is placed on a flask 7 carried by a pattern plate 5, to form a sealed space 40 on a filler 41 which fills the interior of the flask 7. Means are provided for introducing an explosive agent such as a mixture of gaseous fuel 17 and oxygen 18, liquid fuel, powder or the like, into the sealed space 40, as well as means 19 for igniting the explosive agent in the sealed chamber 40, such as a spark plug type igniter. As the explosive agent is ignited, an explosion or rapid combustion takes place to increase the pressure in the sealed space 40, so that a blast of gas is applied to the surface of the filler 41 and penetrates the bed of the filler to be relieved through vent holes 4 formed in the pattern plates, as well as in the pattern 2 carried by the pattern plate 5, so that the filler 41 is compacted to form a mould of a desired compactness. <IMAGE>

Description

SPECIFICATION Moulding method and apparatus The present invention relates to a moulding method and apparatus, particularly to a moulding method and apparatus for forming a mould easily and rapidly without generating violent vibrations.

There have been proposed and developed various moulding methods, for example the jolt-type method, the squeeze-type method and the combined jolt-squeeze-type method. These conventional methods, however, present the following problems.

The jolt-type method inevitably produces violent vibrations which continue for 4 to 5 seconds or longer giving violent shock to any people in the vicinity - so-called environmental disruption. In addition, the jolt-type moulding machine is required to have a sturdy and massive construction in order to withstand the very large number of cycles of impacts which cause the vibration. Also, it takes a considerably long time to form a mould with this type of moulding machine.

In the squeeze-type method the desired hardness or tightness of the mould often fails due to poor compaction of the moulding sand, particularly when the pattern plate has a complicated form. However, the vibration is not so severe as compared with jolt-type method.

Further, the jolt-squeeze-type method involves the same drawback as the aforementioned jolt-type method and requires a large-scale and complicated moulding apparatus.

We have now devised a method of moulding and an apparatus, by which a mould can be produced easily and promptly without violent vibration, there by overcoming the drawbacks of the prior art.

Thus, the present invention consists in a method of producing a mould in which compaction of a filler at a pattern is at least partially achieved by subject ing the filler to a rapid gas pressure increase resulting from combustion or explosion.

The invention also consists in an apparatus for producing a mould, which can provide a gas-tight chamber at a pattern, and has ignition means for igniting an explosive or combustible material in the chamber to compact, by resulting gas pressure, filler at the pattern.

The invention will now be illustrated in more detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a vertical sectional view of a moulding apparatus in accordance with an embodiment of the invention; and Figure2 is a vertical sectional view of a moulding apparatus in accordance with another embodiment of the invention.

Referring first to Figure 1, a moulding apparatus has a flat table 1 having a central opening 2 of suitable size, and is placed on a base preferably supported by legs, which are not shown. A pattern plate 5 mounted on the table 1 carries a pattern 3 and is provided with small vent holes 4 formed at portions where the compaction of the moulding sand would be poor. The small vent holes 4 are open at their lower ends to the opening 2, and are provided at their upper ends with vent plugs 6.

The pattern plate 5 carries a flask 7 of height greater than that of the pattern 3, and which can move up and down. A cover member 9 is provided on the flask 7 with a sealing member 8 between them, to close the upper opening of the flask 7 in a gas-tight manner. The cover member 9 can be moved up and down by, for example, a known lifting mechanism, omitted from the drawings.

The cover member 9 is provided with a supply port 10 through which a gas mixture gas or other fuel can be introduced into the sealed space 40 formed between the cover member 9 and the flask 7. The supply port 10 communicates with a gas fuel cylinder 17 through a stop valve 11, flexible conduit pipe 12, branch pipe 13 and regulator valve 15.

Another branch pipe 14 also branches from the flexible conduit pipe 12 for connection to an oxygen cylinder 18, via a regulator valve 16. A spark plug or other type of igniter 19 is attached to the cover member 9 and projects into the aforementioned sealed space 40. A spark plug type igniter 19 may be electrically connected to one end of a D.C. power supply 23 through lines 20, 21, via a switch 22, while the other end of the D.C. power supply is earthed to the cover member 9. In this way a spark can be generated between the cover member 9 and the igniter 19 as the switch 22 is closed.

The space defined by the pattern plate 5 and the flask 7 may be filled with ordinary green sand 41.

The regulator valves 15, 16 may be suitably adjusted to provide at the desired rate a gaseous mixture of the fuel gas and oxygen from the cylinders 17, 18, of the desired composition. The gaseous mixture is introduced into the conduit pipe 12 and, when the stop valve 11 is opened, into the sealed space 40 defined by the flask 7 and the cover member 9. After closing the stop valve 11, the switch 22 is turned on to generate a spark at the igniter 19, so that the gaseous fuel mixture in the sealed space 40 is ignited to explode or burn thus generating a high pressure in the sealed space 40. Consequently, the resulting blast of gas forcibly flows through the bed of green sand 41 towards the vent plugs 6 and is discharged through the small vent holes 4.In consequence, the green sand 1 is displaced toward the vent plugs 6, 6 and is compacted to a high density, not only at portions where there was poor compaction of the sand but also at portions along the surface of the pattern plate 5. At the same time, the green sand in the upper portion of the sand bed is pressurized and compacted to a comparatively high density, so that the whole part of the bed is hardened to the desired degree of hardness.

Then, the cover member 9 is lifted by, for example, the aforementioned lifting device, and the flask 7 is also lifted by a rapping device (not shown) for pattern drawing. Subsequently, after moving the flask 7 incorporating the mould away from the pattern plate 5, a new empty flask 7 may be placed on the pattern plate 5 and a new batch of green sand 41 charged into the flask 7. Then, the cover member 9 is placed again on the new flask, and the complete operation repeated.

The compact distribution of green sand 41 in the flask 7 is determined by various factors, such as the positions and number of the vent plugs 6, the mixing ratio of fuel gas and oxygen and the amount of fuel mixture introduced.

Figure 2 shows an alternative moulding apparatus, which is suitable for use where the green sand 41 of the upper part of the sand bed has to bd further compacted and hardened. In this case, the cover member 9a is further provided with a downwardly directed cylinder 25 having a piston rod 26 received in a gas-tight manner by a bore of the cover member 9a. A squeeze plate 27 is fixed to the lower end of the piston rod 26. After penetration of the expanded gas, the cylinder 25 may be actuated by, for example, another pressure source or like means to lower the squeeze plate 27 to press and compact the green sand 41.

Although the expansion and explosion take place in the sealed space 40 in the apparatus described, this is not essential and the explosion or rapid combustion may occur in another chamber, and the blast of gas be introduced into the sealed space 40 through a pressure-resistant conduit. Also, an equivalent effect may be obtained by using kinds of fuel other than gaseous fuel, e.g. liquid fuels, explosives and the like.

As'has been described a blast of gas is applied to the surface of filler filling the flask, carried by a pattern plate having a multiplicity of small vent holes, so that the gas is made to penetrate the bed of the filler material and flow toward the small vent holes to compact the filler. It is, therefore, possible to form a strong mould easily and rapidly, even when the pattern on the pattern plate has a complicated shape, while eliminating the unfavourablevibration which continues more than 4 to 5 seconds in the case of conventional jolt-type moulding methods.

Claims (18)

1. A method of producing a mould in which compaction of a filler at a pattern is at least partially achieved by subjecting the filler to a rapid gas pressure increase resulting from combustion or explosion.

2. A method according to claim 1, in which gas, after combustion or explosion, penetrates the filler and is at least partially discharged through vents in the pattern.

3. A method according to claim 1 or claim 2, in which an explosive agent or mixture is introduced into a sealed space at the filler, and is ignited to cause an explosion in the sealed space.

4. A method according to claim 1 or claim 2, in which a blast of exploded gas is introduced into a sealed space at the filler.

5. A method according to any one of claims 1 to 4, in which the filler is mechanically compressed by a squeeze plate after the pressure increase.

6. An apparatus for producing a mould, which can provide a gas-tight chamber at a pattern, and has ignition means for igniting an explosive or combustible material in the chamber to compact, by resulting gas pressure, filler at the pattern.

7. An apparatus according to claim 6, having a pattern with vents for discharge of gas after combustion or explosion.

8. An apparatus according to claim 7, in which the gas-tight chamber is defined by a flask, the pattern and a cover.

9. An apparatus according to any one of claims 6, 7, and 8, having a port for supply of explosive or combustible material to the gas-tight chamber.

10. An apparatus comprising: a pattern plate provided with a plurality of vent holes; a flask which can be combined with the pattern plate; a cover member for closing in a gas-tight manner the opening of the flask combined with the pattern plate to form a sealed space on the surface of filler filling said flask; and at least a port through which a blast of exploded gas can be introduced into said sealed space.

11. An apparatus according to any one of claims 6to 10, having a squeeze plate mounted on a cover, which can further compress filler at the pattern.

12. An apparatus according to claim 7, having a piston rod which can actuate the squeeze plate, a through bore formed in the cover, slidably receiving the piston rod, and a cylinder mounted on the cover which can drive the piston rod.

13. An apparatus according to any one of claims 6 to 12, having a sealing member on a peripheral wall of a flask around an opening of the flask, and means for moving a cover up and down relative to the flask.

14. An apparatus according to any one of claims 6to 13, having a pattern plate on which the pattern can be mounted, the pattern plate having vents for discharge of gas after explosion or combustion.

15. A method of producing a mould substantially as herein described with reference to either of the accompanying drawings.

16. An apparatus for producing a mould substantially as herein described with reference to either of the accompanying drawings.

17. A mould produced by a method according to any one of claims 1-5 and 15, or using an apparatus according to any one of claims 6-14 and 16.

18. A casting, cast using a mould according to claim 17.