GB2048142A

GB2048142A - Process and apparatus for forming a sand mould

Info

Publication number: GB2048142A
Application number: GB7929995A
Authority: GB
Original assignee: Sintokogio Ltd
Current assignee: Sintokogio Ltd
Priority date: 1979-05-08
Filing date: 1979-08-30
Publication date: 1980-12-10
Also published as: ZA794559B; AU514819B2; BR7905523A; PH18462A; FR2455937B1; SE438802B; DK360679A; DK171196B1; IT1162654B; SE7907154L; IT7950120A0; CH644537A5; JPS55147462A; DE2933869A1; CA1127823A; AU5004579A; GB2048142B; DE2933869C2; FR2455937A1

Abstract

Sand 23 in a space defined by a squeeze plate 5, a drag up-set frame 1, a drag moulding flask 16 and a pattern plate 17 is made to conform properly to the shape of the pattern plate by means of gas passed through holes 7 in the squeeze plate. Gas escapes through holes 21 in the pattern plate 17. Firstly, the pressure of gas lifts the sand upwards into the recesses of the pattern plate 17, and then the pressure of gas is increased to consolidate the sand in the recesses. Then, the squeeze plate 5 is raised to mechanically compact the whole of the sand. The pattern plate 17 may be shaped on both of its sides to produce a drag mould below and a cope mould above. <IMAGE>

Description

SPECIFICATION Process and apparatus for forming a sand mould The present invention relates to a process and apparatus for forming a sand mould, particularly a drag mould part. The method is based on the following steps: compressed air is passed through moulding sand held in a moulding flask and pattern plate to compact and consolidate the sand; and the moulding sand is then squeezed by a squeeze plate.

Problems have been encountered producing cope and drag mould parts by this type of method, especiaily when using a mach plate type pattern.

When a high pressure is used to float and move the moulding sand towards the recesses defined by the pattern plate or by the pattern plate together with the moulding flask, the moulding sand does not become sufficiently well attached to the pattern plate. Conversely, when the sand is floated under a low pressure, the sand at the pattern plate is not compacted to a sufficiently high density, and as a result the mould does not have sufficient hardness. As a result, it has been considered impossible to make properly a complicated drag mould part simultaneously with a cope mould part by this type of method.

We have now discovered a way in which these problems can be overcome, and the present invention consists in a process for producing a sand mould such as a drag part, which comprises: (a) passing gas at a lower pressure upwards through sand in a mould to fill properly with sand an upper portion of the mould, and then (b) at a higher pressure to compact the sand in the upper portion of the mould; and then (c) moving the squeeze plate upwards to provide a base for the compacted sand.

The squeeze plate is preferably moved sufficiently far to compact the sand further. If desired, the process may additionally comprise passing a gas through the sand after step(b) at a lower pressure than in step (b).

The mould that holds the sand is preferably assembled by fitting the squeeze plate into a drag up-set frame. aligning a drag moulding flask with the frame above the frame, and upwardly moving the frame to meet the flask. If this arrangement is employed, the sand to be moulded may be added to the frame before the flask is aligned with the frame, or afterwards.

The upper portion of the mould is preferably defined by a separate pattern plate. The pattern plate should be provided with vents to allow the gas to escape. The vents are preferably positioned in those parts of the pattern plate of most intricate shape. Also, the squeeze plate should be provided with vents through which the gas can be passed into the chamber defined by the squeeze plate, the pattern plate, mould flask and optional up-set frame. After the sand mould has been compacted, the pattern plate may be removed from the remainder of the device by means of compressed air passed through the pattern plate in the reverse direction to that employed during compression of the sand.

The invention also consists in apparatus for producing a sand mould, which comprises: a mould in which sand can be held, which has an upper portion within which the sand will be shaped having vents to allow passage of gas; and a squeeze plate slideable within the mould, and having holes through which gas can be passed to conform properly the sand in the mould to the upper portion of the mould and to compact such properly conformed sand.

The invention will now be further illustrated with reference to the accompanying drawings which show partial sectional views of various stages of the mould-making process.

A drag up-set frame 1, vertically movable by cylinders 2, has a lower opening in which a squeeze plate 5 can be moved by an upwardly movable piston rod 4. A seal 5a is provided to ensure an air-tight fit between the periphery of the squeeze plate 5 and the up-set frame 1. A chamber 6 exists in the squeeze plate 5, and holes 7 are provided in an upper wall and a hole 8 in a lower wall for the passage of gas through the plate. A source of compressed air is connected to the hoie 8 via a flexible conduit 9 and a main piping system 12.The main piping system 12 includes a shut-off valve 10 and a flow-regulating valve 1 A piping system 13, which itself contains a shut-off valve 1 Oa and flow-regulating valve 1 a, by-passes the valves 10,11. This first by-pass system 13 is in turn bypassed by a piping system 14. As before, piping system 14 has a shut-off valve 1 Ob and a flow-regulating valve 11 b. The particular arrangement of pipe joints is preferably as illustrated in Figure 1.

Two hollow roller conveyors 1 5 are positioned above the drag up-set frame 1 and are spaced sufficiently far apart that the frame can pass between them. A drag moulding flask 16 can be moved to and from a position above the up-set frame by means of these conveyors. A match plate type pattern 1 7 is provided on the moulding flask 1 6 and the pattern 1 7 can be moved away from the moulding flask 1 6 in the upward direction as illustrated in the drawings.Any intricate pattern to be moulded may be defined by the pattern 17 or by the pattern in conjunction with the moulding flask 16, and the particular arrangement illustrated has recesses 1 8 and 1 6. It is these types of recess that are difficult to fill properly with moulding sand. The pattern illustrated consists of a lower pattern and an upper pattern having a chamber 20 between them. The chamber 20 communicates with the outside via narrow passages 21. These narrow passages are positioned in the recesses of the mould; a higher density of holes should be provided in those parts of the mould having tighter recesses. Vent plugs, not shown, should be provided in each hole.

When the apparatus is in operation, flowregulating valve 11 is adjusted to supply compressed air or other gas through the squeeze plate 5 at such a rate that moulding sand 23 is raised slowly. Then, regulating valve 1 a is adjusted so that the rate of supply of compressed air is large enough to generate a high pressure in the moulding sand 23, thus overcoming pressure losses in the sand and passages 21. Regulating valve 11 b is then adjusted to supply air at such a rate that the moulding sand 23 is prevented from dropping.

A cope moulding flask, an upper drag up-set frame, and an upper squeeze plate may be mounted on the pattern plate 17. For clarity, however, these items are omitted from the drawings and from this description of the drawings. Operation of the apparatus will therefore be described on the assumption that only a drag sand mould is to be produced.

The drag moulding flask 1 6 is moved by conveyors 1 5 to a position immediately above the drag up-set frame. A squeeze plate 5 is then fitted within the frame. Cylinders 2, 3 are then actuated to move upwards both the up-set frame and the squeeze plate. This upward movement is preferably continued until the moulding flask 16 is just clear of the roller conveyors 1 5. The requisite amount of moulding sand 23 is then delivered from, for example, a hopper (not shown) into the space defined by the frame 1, the squeeze plate 5 and the moulding flask 16. Then, a pattern plate 17 is moved into position above the drag moulding flask 1 6. Cylinders 2, 3 are then actuated again to force the moulding flask 1 6 against the lower surface of the pattern 1 7, as shown in Figure 1.Incidentally, the pattern plate 1 7 illustrated has a particular relief both on its upper surface as well as on its lower surface such that a cope mould can be formed in addition to the drag mould.

Valve 10 is opened for sufficient time that compressed air can flow to the moulding sand 23 via conduit 9, feed bore 8, chamber 6 and air flow bores 7. This flow or compressed air moves the moulding sand 23 upwardly at a low speed. The moulding sand 23 will then easily flow into any recess, such as recess 1 8, having air vents at its base. The air is then discharged via the passages 21 and chamber 20. This method ensures that the moulding sand impinges strongly on any projections of the pattern plate 17 and is thereby forced into corresponding recesses without being solidified. As a resuit the density-of moulding sand in the recesses can be increased.

Valve 10 is then closed and valve 1 Oa is opened for a particular length of time.

Compressed air then flows via the same route as before but to generate a higher pressure under the moulding sand 23. This causes the density of the sand close to the surface of the pattern plate 1 7 to be increased and the sand to be solidified. This stage of the operation is shown in Figure 2.

The next stage is shown in Figure 3, where the valve 1 Oa has been closed, the valve 1 Ob opened, and piston rod 4 extended to move the squeeze plate 5 to the base of the moulding sand 23. The squeeze plate is preferably moved to further compact the moulding sand as a whole. The moulding sand is then prevented from falling by the opening of shut-off valve 1 Ob, and this condition is maintained until the squeezing operation by plate 5 has begun. The second bypass piping 1 4 and its associated valves may be omitted if there is no danger of the moulding sand dropping from its raised position.

This mechanical squeezing of the whole of the sand by the squeeze plate 5 is carried out primarily to consolidate that part of the sand which is not compressed by the action of the compressed air alone. However, this mechanical squeezing has some effect on the highly compressed parts produced by the compressed air.

The sand drag mould is now complete and operation of cylinders 2, 3 may be reversed to lower the drag up-set frame 1 and the squeeze plate 5. The drag moulding flask 1 6 may then be removed from the pattern 17 and lowered onto the roller conveyors 1 5.

Removal of the moulding flask may be achieved by introducing compressed air onto the top of the moulding sand 23 via passages 21. A further piping system 1 4a plus 3-way tap 1 Oc may be connected between the passages 21 and the bypass system 1 4 for this purpose. The up-set frame 1 and the squeeze plate 5 may be separated from the moulding flask 1 6 after they have been lowered slightly.

The drag moulding flask and the sand mould within it may then be transferred elsewhere on the rollers without being inverted. The drag mould part may then be joined to an upper or cope mould part to form a complete mould. As mentioned above, the upper mould part could be formed on a pattern plate 17, but description of this will be omitted. After the drag moulding flask plus its sand mould have been removed from the rest of the apparatus, a fresh empty flask may be introduced and the process repeated any desired number of times.

Although it is preferred that the squeeze plate 5 forces the sand from within an up-set frame into a separable moulding flask, it is possible to use a 1piece moulding flask. The effect of this is, essentially, to eliminate the up-set frame. If this arrangement is used, it will generally be desirable to remove the final sand mould from the moulding flask 16.

This description relates to a preferred apparatus and method and certain modifications can of course be made. For example, it does not matter whether it is the flow rate or the pressure of the compressed air through the squeeze plate 5 that is regulated. Also, the valve 10 need not be closed simultaneously with the valve 1 Oa, as was described above.

The method of the present invention is especially useful for producing a drag mould part using a match plate type pattern. The drag mould part can be produced and can be joined without being inverted, and this can reduce or eliminate any damage due to handling.

Claims

1. A process for producing a sand mould, which comprises: (a) passing gas at a lower pressure or flow rate upwards through sand in a mould to fill properly with sand an upper portion of the mould; and then (b) at a higher pressure of flow rate to compact the sand in the upper portion of the mould; and then (c) moving a squeeze plate upwards to provide a base for the compacted sand.

2. A process according to Claim 1, in which the squeeze plate is moved sufficiently far to compact the sand further.

3. A process according to Claim 1 or Claim 2, which additionally comprises passing a gas through the sand after step (b) at a lower pressure than in step (b).

4. A process according to any one of the preceding Claims, in which the mould which holds the sand is assembled by fitting the squeeze plate into an up-set frame; aligning a moulding flask with the frame above the frame; and upwardly moving the frame to meet the flask.

5. A process according to Claim 4, in which sand is added to the frame before the flask is aligned with the frame.

6. A process according to any one of the preceding Claims, in which the upper portion of the mould which holds the sand is defined by a pattern plate.

7. A process according to Claim 6, in which the pattern is removed from the sand mould by pressure of gas passed through bores in the pattern plate.

8. A process for producing a drag sand mould according to any one of the preceding Claims.

9. A process for producing a drag sand mould and a cope sand mould using a single pattern plate, in which the process according to Claim 6 is carried out beneath the pattern plate to form a drag sand mould, and a corresponding but vertically inverted process is carried out above the pattern plate to form a cope sand mould.

10. An apparatus for producing a sand mould, which comprises: a mould in which sand can be held, which has an upper portion within which the sand will be shaped having vents to allow passage of gas; and a squeeze plate slideable within the mould, and having holes through which gas can be passed to conform properly sand in the mould to the upper portion of the mould and to compact such properly conformed sand.

1 An apparatus according to Claim 10, in which the upper portion is defined by a pattern plate having vents for passage of the gas.

12. An apparatus according to Claim 11, in which the mould in which sand can be held comprises: the pattern plate, a mould flask, and an up-set frame; the flask being movable vertically so that it can be joined to and separated from the pattern plate.

13. An apparatus for producing a drag sand mould according to Claim 12, in which the mould flask is a drag mould flask.

14. An apparatus for producing a drag sand mould and a cope sand mould, which comprises: a pattern plate, a mould for sand above the pattern plate for forming the cope sand mould, a mould for sand below the pattern plate for forming the drag sand mould; and a squeeze plate slideable within each mould for sand; the squeeze plate and pattern plate having holes for the passage of gas into the moulds for sand to properly fill them with sand and to compact the sand.

1 5. An apparatus according to Claim 14, in which each mould for sand comprises a mould flask and an up-set frame; the squeeze plate being slideable within the up-set frame.

1 6. A method of producing a drag mould part, comprising the steps of placing moulding sand in a space defined by a moulding flask and a squeeze plate slideably disposed in said drag moulding flask, said squeeze plate being provided with a means for blowing compressed air in the upward direction, joining a pattern having a plurality of air discharge bores to the upper end of said drag moulding flask in which the moulding sand is placed, blowing first compressed air from said blowing means provided in said squeeze plate so as to move the moulding sand upwardly toward said pattern, blowing from said blowing means second compressed air at a flow rate or pressure greater than that of said first compressed air so as to increase the density of the moulding sand in the vicinity of said pattern, and upwardly moving said squeeze plate to squeeze the moulding sand as a whole.

1 7. A method according to Claim 16, wherein the moulding sand is placed in a space defined by said drag moulding flask, a drag up-set frame disposed below said drag moulding flask and said squeeze plate which is fitted in said drag up-set frame.

18. An apparatus for producing a drag mould part, comprising a vertically movable drag moulding flask, a squeeze plate slideably fitted in said drag moulding flask, a pattern having a plurality of air discharge bores and arranged to fit in said drag moulding flask, means for carrying said pattern above said drag moulding flask, means for upwardly moving said drag moulding flask to fit the same with said pattern thereon, means, provided in said squeeze plate, for blowing compressed air, and means for selectively feeding to said flowing means compressed air at a different flow rate or pressure, respectively.

19. An apparatus according to Claim 18, wherein said squeeze plate has a chamber therein: said blowing means is provided in the upper surface of said squeeze plate and consists of a plurality of air discharge bores communicated with said chamber; and said blowing means is communicated with said chamber.

20. An apparatus according to Claim 18, wherein said feeding means has a compressed air source, a plurality of piping systems for communicating said compressed air source with said blowing means, each of said piping systems having a shut-off valve and a flow or pressure regulating valve so as to feed air each piping system having different flow rate or pressure from each other.

21. An apparatus according to Claim 18, wherein said squeeze plate is provided with an airtight seal around the peripheral wall thereof and air tightly fitted in said drag moulding flask.

22. An apparatus according to Claim 18, wherein means for selectively connecting said feeding means to means for allowing compressed air to pass through said air discharge bores in said pattern into said bottom moulding flask, thereby to make easier to remove said pattern from said drag mould part which has been completed.

23. An apparatus for producing a drag mould part, comprising a vertically movable drag up-set frame, a squeeze plate slidably fitted in said drag upset frame, means for bringing a drag moulding flask in a position above said drag up-set frame, a pattern having a plurality of air discharge bores and arranged to fit in said drag moulding flask, means for transferring said pattern above said drag moulding flask which has been brought in the position, means for upwardly moving said drag upset frame with said squeeze plate fitted therein so as to allow said drag moulding flask to be placed thereon and to allow said pattern to be placed on said drag moulding flask in alignment therewith, means, provided on said squeeze plate, for blowing compressed air onto said pattern, and means for selectively feeding to said blowing means compressed air at a different flow rate or pressure, respectively.

24. Apparatus for forming a sand mould substantially as hereinbefore described with reference to the accompanying drawings.