SAND VALVE AND SAND SHOT SYSTEM

Abstract: The present invention relates to a sand valve and a sand shot system, in which the sand valve forms a sealable inlet for the sand into a sand storage container of a sand shot system, comprising a sand valve housing, a sand inlet port and a closure member for selectively opening and closing the sand inlet port, whereby the air inlet is arranged such that the "dead" space (4) above the column (9) of sand in the sand storage container is minimised.

Description: SAND VALVE AND SAND SHOT SYSTEM TECHNICAL FIELD The present invention relates to a sand valve of the kind set forth in the preamble of claim 1 and to a sand shot system as set forth in the preamble of claims 10 and 21. BACKGROUND ART A sand valve according to the preamble of claim 1 and a sand shot system according to the preamble of claims 10 and 21 are known from the Disamatic ® service manual 9153 H 1410, version 03/98. Sand shot systems relate to foundry machinery, such as the Disamatic ® mould string plant in which the mould- or core sand is introduced into the mould- or core chamber by means of compressed air. The sand is injected abruptly onto the core- or moulding chamber as a compact mass. The necessary acceleration is imparted to the moulding sand by compressed air creating a pressure wave on the column of sand and forcing it abruptly through a nozzle into the core chamber or mould chamber. Such sand shot systems typically comprise a sand container, generally in the form of a cylinder, a sand valve, generally a dome- or arch-valve, i.e. a valve with a dome- or arch-shaped closure member as known from US-A-4 137 935, a supply of pressurised air and a manifold with inlets for the pressurised air connecting the sand container with the sand valve. The manifold usually comprises means for distributing the pressurised air evenly over the surface of the sand in the sand container. An important aspect in the sand shooting principle is the pressure wave effect of the air acting on the column of sand. Hereto, the sand container is filled up to the maximum level before each shot in order to reduce the "dead" space above the sand column. Further, the sand shot systems are provided with a pressure tank, the contents of which are a multitude of the amount of sand to be shot. It is important that the pressurised air enters the sand storage container as quickly as possible. For this purpose high-speed valves are interposed between the air inlet and the pressure tank that allow the compressed air to enter abruptly into the sand container. DISCLOSURE OF THE INVENTION It is the object of the invention to provide a sand shot valve of the kind referred to above, with which the pressure wave effect of the air acting on the column of sand is improved and which allows a more simple construction of a sand shot system. This object is achieved by the characterising features of claim 1. By providing an inlet for the supply of pressurised air in the sand valve housing itself, the "dead" space above the sand column can be significantly reduced and thereby the pressure wave effect of the pressurised air is increased and the overall consumption of pressurised air is reduced. Further the manifold with the inlets for the pressurised air as used in the prior art becomes superfluous and can be omitted from the sand shot system construction, thus allowing a more simple and economic construction. It is another object of the invention to provide a sand shot system of the kind referred to above, in which the pressure wave effect of the air acting on the column of sand is improved and which sand shot system is simple in construction. This object is achieved by the characterising features of claim 10. By supplying the pressurised air above the lower periphery of the housing of the sand valve, the "dead" space above the sand column can be significantly reduced and thereby the pressure wave effect of the pressurised air is increased and the overall consumption of pressurised air is reduced. Further the manifold with the inlets for the pressurised air as used in the prior art becomes superfluous and can be omitted from the sand shot system construction, thus allowing a more simple and economic construction. It is yet another object of the invention to provide a sand shot system of the kind referred to above, in which the pressure wave effect of the air acting on the column of sand is improved and which sand shot system is simple in construction. This object is achieved by the characterising features of claim 21. By turning the dome- or arch-valve upside-down with respect to the traditional arrangement, the "dead" space above the sand column can be significantly reduced and thereby the pressure-wave effect of the pressurised air is increased. According to an embodiment of the invention, the sand valve housing comprises two or more inlets. According to a further embodiment, the sand valve has dome- or arch-shaped closure member. This embodiment has two sub-embodiments, namely one with the dome- or arch-shaped closure member with its convex surface facing upwardly in the closed position, and the other sub-embodiment with the dome- or arch- shaped closure member with its convex surface facing downwardly in the closed position. According to another embodiment the sand valve comprises a ring-shaped channel for distributing the pressurised air equally. According to yet another embodiment the sand valve comprises three or four inlets which are arranged tangentially with respect to the circular housing for creating a swirl in the pressurised air above the sand column. Further embodiments are set out in the detailed description and the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS In the following detailed part of the description of the present invention, the invention will be explained in more detail with reference to the exemplary embodiments of the sand valve and the sand shot system shown in the drawings, in which Figure 1 is a side view of a prior art sand shot system, Figure 2 is a side view of a sand shot system according to the invention, Figures 3 and 3a are a cross-sectional views of a sand valve and sand container according to an embodiment of the invention, Figure 4 is a top view on a sand valve according to the invention, Figure 4a is a cross-sectional vie of a valve according to the invention, Figure 5 is a cross-sectional view of a sand valve and sand container according to another embodiment of the invention, Figures 6 and 7 are cross-sectional views of two embodiments according to the "upside-down" arrangement of the valve, and Figure 8 is across-sectional view of another embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION In the apparatus shown in the Figure 2 a sand storage container 5 is adapted to receive mould sand from a sand supply reservoir (not shown), and temporarily to store this mould sand. During the moulding process, air under pressure is supplied to the closed space 4 above the sand, so that the mould sand can be forced downwardly through a sand outlet 7 into a mould chamber (not shown). The pressurised air is supplied from a pressure tank 2, the contents of which are a multitude of the amount of sand to be shot. The supply of pressurised air to the sealed space 4 above the sand is controlled by high-speed air inlet valves 3. Preferably at least two of such valves 3 are used in order to achieve the required capacity. A sand valve 10 is arranged on top of the sand storage container 5 to define a sealable inlet port 17 above the column 9 of sand in the sand storage container 5. After each shot, the sand valve 10 is opened by moving a closure member 12 from a closed position to an open position so that new mould sand may be added until the sand storage container 5 is filled up to the required level. The mould sand level in the sand storage container 5 is monitored by a sand level sensor 6. After the sand shot, the space 4 above the sand column 9 is vented through an air outlet 13 that is preferably arranged the sand valve housing 11. A special relief valve 8 suitable to handle pressurised air contaminated with sand is controlling the relief of the closed space 4 above the sand column 9. The process is thereafter repeated as described above. Such sand shot system is used with mould string apparatus (not shown) comprising a mould chamber. The mould chamber, situated as shown below the sand shot system, is limited in the lateral direction by pattern plates which are supported by a squeeze plate and a pivoted squeeze plate, respectively. With the mould string apparatus box-less mould parts are made from loose green-sand, i.e. sand with moist clay as binder, in the mould chamber defined between a pattern located on a squeeze plate and a pattern located on movable and upwardly pivoted squeeze plate in a downwardly pivoted position of the squeeze plate. In the mould chamber the sand is compacted between the squeeze plate and the pivoted squeeze plate to form a mould part. According to an embodiment of the sand valve and the sand shot system, as shown in Figures 3,3a,4,4a,5 and 6, the air inlets 14 are arranged as a part of the sand valve housing 11 itself. Consequently a manifold 1 is not required in this embodiment of the sand shot system. With this arrangement the sand valve 10 is arranged closer to the top of the sand-column 9 in the sand storage container 5 thereby reducing the "dead" space 4 between the top of the sand column 9 and the sand valve 10. Advantageously, also the air outlet 13 is formed as an integral part of the sand valve housing 11. According to the embodiment shown in figure 5, the sand valve 10 is further provided with a ring-shaped channel 16 for distributing the pressurised air equally over the top of the sand column 9 in the sand storage container 5. The height and shape of the ring-shaped channel 16 are chosen according to circumstances and may follow the shape of the valve housing 11 The closure member 12 of the sand valve 10 is dome- or arch-shaped (arch-shaped closure member not shown). This type of valve is particularly suitable for handling granular materials such as moulding sand. The dome- or arch-shaped closure member 12 co-operates in its closed position with an inflatable seal 18. This kind of valve is reliable for handling granular material that in normal valves leads to malfunctioning of the system. The valve 10 may be arranged so that the dome- or arch-shaped closure member 12 is arranged such that its convex surface is facing upwards in the closed position (Figures 3,3a,4,4a and 5), or according to another embodiment the sand valve 10 may be arranged such that the convex surface of the dome- or arch-shaped closure member 12 faces downwards in the closed position (Figures 6 and 7), in order to reduce the "dead" space (4) above the sand column 9. In the embodiment according to figure 7 the sand valve is arranged "upside down", i.e. with the convex surface of the closure member 12 facing downwards. This arrangement, in combination with a separate manifold 1 for the air inlet 14 and the air outlet 14 provides a sand shot system with a small space 4 above the sand column 9. According to an embodiment of the invention as shown in figure 8, the inlet 14 for the pressurised air is formed by an aperture 19 between the upper edge of the sand storage container 5 and an annular recess in the sand valve housing 11 in which the upper periphery of the sand storage container 5 is received. In this embodiment the valve housing 11 and the sand storage container 5 are movable towards one another and away from one another as indicated by the arrow in figure 8 in order to open and close said aperture to control the supply of pressurised air into the sand shot system. An advantage of this embodiment is that it does not require the use of high-speed air inlet valves. The air inlets and air outlets do not necessarily have to be formed in the valve housing 11, so that the sand valve 10 does not need extensive modification with respect to the known sand valves. According to an embodiment of the invention (not shown), the sand valve 10 comprises three or four inlets which are arranged tangentially with respect to the circular sand valve housing 11 of the sand valve 10. By arranging the inlets 14 in this way a swirl is created in the pressurised air above the sand column 9 for distributing the pressurised air evenly over the sand column 9. LIST OF REFERENCE NUMERALS 1 Manifold 2 Pressure tank 3 Air inlet valve 4 "Dead" space 5 Sand storage container 6 Sand level sensor 7 Sand outlet 8 Relief valve 9 Sand column 10 Sand valve 1 1 Sand valve housing 12 Closure member 13 Air outlet 14 Air inlet 15 Lower periphery 16 Ring-shaped channel 17 Sand inlet port 18 Inflatable seal 19 Aperture

Claims: CLAIMS: 1. Sand valve (10) for forming a sealable inlet for sand into a sand storage container (5) of a sand shot system, comprising a sand valve housing (11), a sand inlet port (17), and a closure member (12) for selectively opening and closing the sand inlet port (17), characterised in that the valve housing (11) comprises an air inlet (14) for the supply of pressurised air for the sand shot. 2. Sand valve (10) according to claim 1, characterised by comprising two or more air inlets (14). 3. Sand valve (10) according to claim 2 or 3, characterised by comprising a ring-shaped channel (16) for distributing the pressurised air equally over the top of the sand column (9). 4. Sand valve (10) according to any of claims 1 to3, cha ra cte ris ed by comprising an outlet (13) for venting the pressurised air after the sand shot. 5. Sand valve (10) according to any of claims 1 to 4, characterised by the closure member (12) being dome- or arch-shaped. 6. Sand valve (10) according to claim 5, characterised in that the dome- or arch-shaped closure member (12) has its convex surface facing upwardly in the closed position. 7. Sand valve (10) according to claim 5, characterised in that the dome- or arch-shaped closure member (12) has its convex surface facing downwardly in the closed position. 8. Sand valve (10) according to any of claims 5 to 7, ch a ra cte ri s ed by comprising an inflatable seal co-operating with the dome- or arch-shaped closure member (12). 9. Sand valve (10) according to any of claims 1 to9, ch a ra cte ri s ed by comprising three or four air inlets (14) which are arranged tangentially with respect to the circular sand valve housing (11) of the sand valve (10) for creating a swirl in the pressurised air above the sand column (9). 10. Sand shot system comprising a sand valve (10), a sand storage container (5) and a source of pressurised air (2) for the sand shot, the sand valve (10) comprising a sand valve housing (11) arranged on top of the sand storage container (5), whereby the sand valve (10) forms a sealable inlet for supplying sand to the sand storage container (5), characterised in that the pressurised air is supplied to the sand shot system above the lower periphery (15) of the housing (11). 11. Sand shot system according to claim 10, cha racteri sed by the sand valve (10) comprising an annular recess in which the upper periphery of the sand storage container (5) is received, whereby an aperture (19) between the upper periphery of the sand storage container (5) and the recess in the valve housing (11) forms the air inlet for the pressurised air into the space (4) above the sand column (9). 12. Sand shot system according to claim 11, characterised in that the sand valve housing (11) and the sand storage container (5) are movable towards one another and away from one another in order to open and close said aperture to control the supply of pressurised air into the sand shot system. 13. Sand shot system according to claim 10, cha ra cteri sed by the sand valve (10) comprising two or more air inlets (14). 14. Sand shot system according to any of claims 10 to 13, characterised by comprising a ring-shaped channel (16) for distributing the pressurised air equally over the top of the sand column(9). 15. Sand shot system according to any of claims 10 to 14, cha ra cteri sed by comprising an air outlet (13) for venting the pressurised air after the sand shot. 16. Sand shot system according to any of claims 10 to 15, cha racterised by the closure member (12) being dome- or arch-shaped. 17. Sand shot system according to claim 16, characteri s e d in that the dome- or arch-shaped closure member (12) has its convex surface facing upwardly in the closed position. 18. Sand shot system according to claim 16, ch a ra cte ri s ed in that the dome- or arch-shaped closure member (12) has its convex surface facing downwardly in the closed position. 19. Sand shot system according to any of claims 16 to 18, characterised by the sand valve (10) comprising an inflatable seal (18) co-operating with the dome- or arch-shaped closure member (12). 20. Sand shot system according to any of claims 10 to 19, cha racteri sed by the sand valve (10) comprising three or four air inlets (14) which are arranged tangentially with respect to the circular sand valve housing (11) for creating a swirl in the pressurised air above the sand column (9). 21. Sand shot system comprising a sand valve (10), a sand storage container (5) and a source of pressurised air (2) for the sand shot, the sand valve (10) comprising a sand valve housing (11) arranged on top of the sand storage container (5), and by a dome- or arch-shaped closure member (12), whereby the sand valve (10) forms a sealable inlet for supplying sand to the sand storage container (5), characteri s e d in that the convex surface of the dome- or arch-shaped closure member (12) faces downwards in the closed position. 22. Sand shot system according to claim 21, cha racteri sed by the sand valve (10) comprising an annular recess in which the upper periphery of the sand storage container (5) is received, whereby an aperture between the upper periphery of the sand storage container (5) and the recess in the housing (10) forms the air inlet (14) for the pressurised air into the space (4) above the sand column (9). 23. Sand shot system according to claim 22, characterised in that the sand valve housing (11) and the sand storage container (5) are movable towards one another and away from one another in order to open and close said aperture to control the supply of pressurised air into the sand shot system. 24. Sand shot system according to claim 21, cha racteri sed by the sand valve (10) comprising two or more air inlets (14). 24. Sand shot system according to any of claims 21 or 24, characterised by comprising a ring-shaped channel (16) for distributing the pressurised air equally over the top of the sand column (9).

Inventors: MOGENSEN VAGN, MOGENSEN, VAGN
Applicants: GEORG FISCHER DISA AS, MOGENSEN VAGN, GEORG FISCHER DISA A/S, MOGENSEN, VAGN
Application year: 1999
Main classification: B22C15
IPC codes: B22C15