WO2002060616A1

WO2002060616A1 - Method and machine for manufacturing sand moulds and down sprue assembly and holding plate to be used by the performance thereof

Info

Publication number: WO2002060616A1
Application number: PCT/DK2001/000071
Authority: WO
Inventors: Kenneth Guldager Christiansen; Torben Hansen
Original assignee: Disa Industries A/S
Priority date: 2001-01-31
Filing date: 2001-01-31
Publication date: 2002-08-08

Abstract

A method and a machine for the moulding of sand moulds. The machine has upper and lower moulding boxes (6, 7) and a telescopic down sprue assembly (11) arranged in the upper moulding box (6). A matchplate (19) with moulding pattern is clamped between upper and lower moulding boxes (6, 7), whereafter the down sprue assembly (11) is activated with pressurised air, so that a telescopic extendable part (18) is forced on to contact with the matchplate (19). The pressurised air is de-activated before the matchplate (19) is removed so that the end (18) of the down sprue (11) remains in position without any sudden movements which severely could damage the upper sand mould (4). The invention also relates to a holding plate for the sprue assembly.

Description

Method and machine for manufacturing sand moulds and down sprue assembly and holding plate to be used by the performance thereof

Field of the invention.

The present invention concerns a method and a machine for the moulding of 0 sand moulds in a moulding machine having upper and lower moulding boxes and having a telescopic down sprue assembly arranged in the upper moulding box during moulding.

The invention also relates to a telescopic down sprue assembly as well as a 5 holding plate for such. Furthermore, the invention concerns the use of pressurised air for providing extension pressure in a down sprue assembly.

Closest prior art.

Methods and machines of the above mentioned art are well-known within the o field of making sand moulds. With today's techniques the sand moulds are subsequently utilized for the industrial casting of metal products with an often highly complex geometry. Conventionally, a matchplate with moulding pattern is clamped between upper and lower sand moulding boxes whereby the lower part of a telescopic compressible down sprue assembly is forced on to contact 5 with the matchplate.

The top plate of the upper moulding box is known as the cope press plate. The bottom plate of the lower moulding box is known as the drag press plate relating to the ready sand mould being removed through the bottom of the o lower moulding box after the sand is being squeezed. The telescopic down sprue assembly constitutes a core for the moulding of the pouring inlet in the upper sand mould, so that the liquid metal later on may enter the moulded form cavity between the upper and lower sand moulds. The upper part of the down sprue assembly is fixed to the lower side of the cope press plate and extends vertically down into the moulding box.

When the lower part of the down sprue assembly is forced on to contact with the matchplate being clamped, the lower part acts against an axial spiral spring within the down sprue assembly.

The moulding boxes are thereafter filled with sand, which is blown or shot into the moulding boxes through openings in the sides thereof. Often, the moulding boxes are turned 90° so that the sand is shot vertically down into both boxes being filled simultaneously. The sand is subsequently being compressed or squeezed vertically by the moving of the cope press plate and the drag press plate in direction against each other. The down sprue assembly is then being further compressed telescopically by the axial travel of the lower part against the internal spiral spring in the down sprue.

Thereafter, the upper and lower moulding boxes are being withdrawn from each other, the matchplate is removed and eventual cores are mounted in the sand moulds before the boxes again are closed against each other. Finally, the closed sand moulds are removed through the bottom of the lower moulding box by the simultaneous lowering of the drag and cope plates and at the same time keeping the sand moulds restrained under a certain pressure between the plates.

Thereafter, the down sprue assembly is lifted up and free of the upper sand mould. The spiral spring keeps the lower part of the down sprue assembly pressed on to the matchplate during the sand shot. The aim is to secure, that the full geometry of the pouring inlet is moulded in the sand and furthermore to avoid, that sand enters the pouring inlet being moulded or enters the cavities of the moulds after the matchplate have been removed. However, when the matchplate is removed, the compressed spiral spring is released, so that the lower part of the down sprue assembly travels a distance free of the inner surface of the sand mould and into the mould cavity. Thereby, particles are unavoidably torn loose by the friction force between the sand and the lower travelling part of the down sprue. Remains of sand particles in the metal product moulded later on are unwanted as they are crucial to strength and quality of the product.

The compression force of the spiral spring is increased by increased telescopic compression of the down sprue assembly, which in part follows the travelling of the cope press plate during the squeezing of the sand. As the squeezing is controlled by the actual pressure build up by the sand it follows, that the actual travelling of the cope press plate is undefined from time to time. Consequently, the compression ratio and thereby the actually exercised compression force of the compressed spring in the down sprue is impossibly to predict from time to time for the particular moulding being performed.

The consequence is, that sometimes the spring is restrained with such a high compression force, that the lower part of the down sprue is released with a force and velocity higher than intended when the matchplate is removed. Fragments or even major parts of the sand mould are broken off around the down sprue and enters the cavity. The matchplate may also be injured by the release of the spring and in worst cases may pattern parts even be broken off. The shape of the lower part of the pouring inlet moulded may certainly be destroyed, so that the later moulding of the metal product in the cavity is influenced. Furthermore, the broken off sand parts remains in the cavity between the sand moulds so that they are taken up into the metal product moulded later on in the cavity. However, even worse is, that the metal product may for sure be weakened. Such metal products with inclusions of sand fragments must always be scrapped as the products suffer lower strength and performance than intended. However, severe problems and even danger may arise if the metal products are used anyway, for example in the case of inner inclusions of sand fragments in the products which are not discovered during quality control.

The construction and calculation of the compression force of the spring in the down sprue assembly is difficult. On the one hand a certain force is necessary at full extended length to preserve the pressure against the matchplate when sand is blown into the upper box at very high velocity. On the other hand, the force must not raise to an excessive level when the spring being compressed with the danger of that the lower part of the down sprue jumps to its extended position damaging the sand mould and the pouring inlet formed. Also must the surface friction with the sand be overcome, and certainly so that when sand particles enters the sliding surfaces of the down sprue, travelling of the parts are secured.

The object of the present invention is to provide a method, a machine as well as a down sprue assembly and a holding plate which avoid the above mentioned drawbacks.

By the method according the present invention is provided the steps of:

clamping a matchplate with moulding pattern between upper and lower moulding boxes, activating the down sprue assembly with pressurised air so that the telescopic extendable part of the assembly is forced on to the matchplate, blowing sand into the moulding boxes, squeezing the sand, deactivating the pressurised air from the down sprue assembly, withdrawing the upper and lower moulding boxes from each other thereafter removing the matchplate.

Hereby is secured, that no sand parts are broken off around the inlet portion of the sand mould when the matchplate is removed.

The down sprue assembly is activated with pressurised air giving it sufficient force against the matchplate, so that no sand enters between the end of the down sprue and the part of the matchplate in contact therewith.

By the deactivating of the pressurised air in the down sprue before withdrawing the mouding boxes from each other, the end of the down sprue in contact with the matchplate looses its pressure force against the matchplate. When the matchplate subsequently is removed, the end of the down sprue rests in place without movement. Consequently without any unwanted and unpredictable pressures to the fragile part of the upper sand mould surrounding the down sprue.

By the subsequent lifting of the down sprue up from the upper sand mould it is secured, that it is free of any possible internal spring force, which as by the prior art could be released when the down sprue is moved so that the end of the down sprue moves with a sudden jump and damages the sand form. By the invention all parts of the down sprue, may there be two or several telescopic parts, just follows with when the down sprue is moved upwardly and free of the sand form. The pressure may advantageously be kept in the range of 0,1 - 10 bar available in most production facilities.

The moulding machine according to the invention comprises a telescopic down sprue assembly with an inner cavity, which is connected with means for providing pressurised air, so that a pressure is created in the cavity.

The operator is now free to control the pressure in the down sprue so that it suits into the process of moulding the sand forms, thereby eliminating the risk of damaging the fragile sand forms or the matchplate by the telescopic movement of the down sprue. By activating the means for providing the pressurised air, the end of the down sprue is under pressure, so that it may be pressed against the matchplate only after the boxes are closed and during the sand shot. Thereafter, the pressure is deactivated, so that the end in contact with the matchplate becomes essentially pressure-less when the matchplate is removed.

Any possibly accumulated compression or spring force in the down sprue, which could be suddenly released as by the prior art is avoided.

Fully in line with the core of the inventive idea the telescopic down sprue assembly has an inner cavity, the opening to which is adapted to be connected with means for providing pressurised air to the cavity for building up, internal pressure.

The known down sprue assembly may advantageously be modified by removing the axial spring from the inner cavity and furthermore creating an opening into the cavity for connection with pressurised air. By finally modifying it, so that one is sure that building up of an internal pressure in the cavity is possible, the inventive down sprue assembly is provided. By the activation of the pressurised air the end or the lower part of the down sprue may simply be activated with an outwardly directed pressure force whenever wanted. This implies, that the pressure force may also be deactivated whenever wished.

When the slidable engagement between the parts of the down sprue assembly features a gap in the range of 0,01-0,50 mm, the gap is kept essentially free from sand particles when the cavity of the down sprue is pressurised. A self- cleaning effect is experienced.

Also the inventive holding plate for the fixation of the inventive down sprue assembly is in line with the core of the invention. It comprises a mounting opening, which via at least one channel arranged in the holding plate is adapted to be connected with means for providing pressurised air to the down sprue.

The holding plate is simply mounted at the lower side of the cope press plate, so that modifications of the latter is avoided for the provision of the pressurised air to the down sprue.

Especially advantageously is when the holding plate comprises at least two mounting openings connected by channels, and which openings are closed off by airtight plugs. After the holding plate has been mounted to the cope press plate the plug at the desired position is removed and the down sprue is mounted in the opening. The remaining plugs are left in the remaining mounting openings so that they are airtight when the pressurised air is present in the channels of the holding plate and in the cavity of the down sprue.

Low manufacturing costs are experienced when the channels are arranged as grooves in the upper surface of the holding plate, which is sealed off when the plate is mounted to the cope press plate, for example by the upper surface of the holding plate being covered by a sealing layer.

The inventive use of pressurised air for providing extension pressure in the cavity of a telescopic down sprue assembly used in a sand moulding machine is furthermore in line with the core of the present invention.

Description of the drawing. The invention will be explained more fully below with reference to the drawing, in which

Fig. 1 is a perspective view of a moulding machine according to the invention,

Fig. 2 - 7 are lateral, sectional views of the schematically shown squeezing and sand shot section of the machine in fig. 1 , performing the method according to the invention,

Fig. 8 is a lateral, sectional view of the down sprue assembly according to the invention,

Fig. 9 is a perspective view of the holding plate according to the invention,

Fig. 10 is a lateral, sectional view of the holding plate in fig. 9, and

Fig. 11 is a lateral, sectional view of the holding plate mounted on the cope press plate of the moulding machine according to the invention. Detailed description of an advantageous embodiment.

The moulding machine 1 shown in Fig. 1 comprises a squeezing and sand shot section 2 for the moulding of sand moulds 4, 5, as well as further sections for the control and manoeuvring of the machine, not being depicted as they constitute part of the well-known prior art within the field. In relation to the machine 1 is arranged a conveyor 3 for the transportation of the closed sand moulds 4, 5 on to further manufacturing steps, such as the moulding of the metal products.

For clarity reasons the moulding machine is shown schematically without details having no importance to the explanation of the present invention. Furthermore, apart from the additive features according to the solution of the present invention, the machines are well-known within the present field.

The squeezing and sand shot section 2 comprises upper and lower moulding boxes 6, 7, which are fixed to and guided by a swingframe 8. By the activation of the swingframe 8 the moulding boxes 6, 7 may be moved in vertical direction in known manner. Beside the swingframe 8 is schematically shown the sand container 9. A security covering door 0, which has been drawn to left so that the squeezing and sand shot section 2 is revealed, is off course closed during production.

The moulding machine according to the invention comprises an inventive telescopic down sprue assembly 11 arranged in the upper moulding box 6 as depicted at the schematically shown squeezing and sand shot section 2 of the machine in fig 2-7.

The telescopic down sprue assembly 11 has an inner cavity 12 as depicted in fig. 8. According to the inventive idea, the cavity 12 is connected with means 13 for providing pressurised air, so that a pressure is created in the cavity 12. The means 13 could typically be a compressor for providing pressurised air with a pressure in the range of 01 , - 10 bar but normally a source of pressurised air is ready available in production facilities. The source 13 for pressurised air is easily connected by a conduit 14 with the inner cavity 12 of the down sprue assembly 11. By means of a valve 15 connected via a wire 16 with a controlling unit or computer 17 pressurising of the inner cavity 12 of the down sprue 11 may be affected and by closing the valve the cavity is de- pressurised. The valve may advantageously comprise a throttle for the outlet of the air when the cavity is being de-pressurised.

The operator is now free to control the pressure in the down sprue 11 by the controlling unit or computer 17. The activation or the deactivation of the pressure in the cavity may thereby be performed, so that it suits timely into the process of moulding the sand forms. By activating the means 13 for providing the pressurised air, the end 18 of the down sprue 11 is under pressure, so that it may be pressed against the matchplate only after the boxes 6, 7 are closed and during the sand shot and the subsequent squeezing of the sand. Thereafter, the pressure is deactivated, so that the end 18 in contact with the matchplate becomes essentially pressure-less when the matchplate is removed. Thereby eliminating the risk of damaging the fragile sand forms 4, 5 or the matchplate 19 by the telescopic movement of the down sprue 11. Any possibly accumulated compression or spring force in the down sprue, which could be suddenly released as by the prior art is thereby avoided.

The considerable advantage of the core of the invention is, that the activation or the deactivation of the pressure force on the lower part 18 of the down sprue assembly is optional, however to be performed within the limits of the solution of claim 1. Furthermore, the strength of the pressure force, which the lower end 18 of the down sprue exerts on to the matchplate is optional as well. By regulating the actual pressure of the pressurised air, the strenght of the pressure force is conveniently regulated to the desired and pre-calculated level.

By the prior known down sprue assembly's the force exerted by the lower end to the matchplate is determined by the size and compression strength of the axial spring in the cavity. However, by the present invention the force exerted by the lower end of the down sprue is optional in strength and level as well as when it is to be applied within the solution of claim 1.

The inventive method comprises the initial step of clamping a matchplate 19 with moulding pattern between upper and lower moulding boxes 6 and 7 as shown in fig. 3. From figure 2 to figure 3 the press simply moves the boxes 6 and 7 vertically in direction against each other until the matchplate 19 is securely clamped.

At the clamping position of fig. 3 the telescopic extendable part or the lower end 18 of the down sprue assembly 11 is activated with pressurised air according to the inventive method. Consequently, the lower end 18 is forced on to contact with the matchplate 19 for providing a core for the inlet in the upper sand mould 4.

Normally, the swingframe 8 turns the closed moulding boxes 6, 7 and the clamped matchplate 90° around from the position shown in figure 3 and to the position shown in figure 4. Openings 20, 21 arranged in the sides of the moulding boxes 6, 7 are thereby turned to a position just below the sand container 9.

At fig. 4 is shown the further step of sand 22 being shot or blown under high pressure from the sand container 9 and simultaneously via the openings 20, 21 into the upper moulding box 6. and the lower moulding box 7. During this step the pressure of the pressurised air is kept in the cavity 12 of the down sprue 11 , so that the end 18 thereof remains firmly pressed on to the matchplate without sand entering there between.

Thereafter, the step of squeezing the sand is performed as pressing means arranged in relation to the swingframe 8 moves the cope press plate 23 and the drag press plate 24 simultaneously in direction against the matchplate 19. As the distance between the cope press plate 23 and the matchplate 19 becomes smaller during the pressing, the down sprue is compressed telescopically the same distance. However, the same predetermined counter pressure remains in the cavity12 whatever the position of the end 18 is. The size of the pressure force acting against the end 18 of the down sprue is thereby independent of the position of the end 18 to the contrary from the prior art having the compressed spiral spring in the cavity.

After the squeezing of the sand the sand moulds 4, 5 are ready moulded. The pressurised air is deactivated from the cavity 12 of the down sprue assembly 11 , and the upper and lower moulding boxes 6, 7 are withdrawn from each other, so that the matchplate 19 may be removed.

By the deactivating of the pressurised air in the down sprue before withdrawing the mouding boxes 6, 7 from each other the end 18 of the down sprue 11 in 5 contact with the matchplate 19 looses its pressure force against the matchplate 19. Hereby it is secured, that no sand parts are broken off around the inlet portion of the sand mould when the matchplate is removed as depicted in figure 5. When the matchplate is removed, the end of the down sprue rests in place without movement and consequently without any unwanted and o unpredictable pressures to the fragile part of the upper sand mould surrounding the down sprue.

After having removed the matchplate 19, eventual cores may be arranged in the cavity of the moulds 4, 5 before the moulding boxes 6, 7 again are closed by the vertical movement of the pressing means at the swingframe 8 to the position depicted in figure 6.

By the subsequent lifting of the down sprue up from the upper sand mould 4 as shown in figure 7, it is furthermore secured, that the end 18 is free of any possible internal spring force, which as by the prior art could be released when the down sprue is moved. By the prior art the end of the down sprue moves with a sudden jump and often damages the sand form. By the invention all parts of the down sprue, may there be two or several telescopic parts, just follows with when the down sprue is moved upwardly and free of the sand form 6.

The closed sand moulds 4, 5 are thereafter transferred to the conveyor 3 for transportation to the next production step such as the moulding of the metal products in the moulds.

After the moulds have been removed the pressurised air may again be activated, so that eventual sand particles in the gap between the telesopically sliding parts of the down sprue assembly is cleaned out before the next moulding process.

The above method have been described with reference to an example where only one down sprue is mounted to the cope press plate. However in the case of two or more down sprue assembly's mounted to the cope press plate the inventive idea may also apply. This could be the case when there are used more than one matchplate during the moulding, or if the matchplate are sectioned in two or more parts.

The inventive down sprue assembly 11 shown in figure 8 may advantageously be provided by modifying a prior known down sprue by removing the axial spring from the inner cavity and furthermore creating an opening 25 into the cavity for connection with pressurised air. By finally modifying, so that one is sure, that building up of an internal pressure in the cavity 12 is possible, the inventive down sprue assembly is provided.

By the activation of the pressurised air the end 18 or the lower part of the down sprue may simply be activated with an outwardly directed pressure force whenever wanted. This implies, that the pressure force may also be deactivated whenever wished.

When the slidable engagement between the upper part 31 and the lower end or part 18 of the down sprue assembly features a gap in the range of 0,01-0,50 mm, the gap is kept essentially free from sand particles when the cavity 12 of the down sprue is pressurised. A self-cleaning effect is experienced.

In figures 8 and 11 the telescopic down sprue assembly is disclosed in an embodiment where it comprises two parts, i.e. the upper part 31 and the lower part 18 which are telescopically movable in relation to each other. However, generally the inventive down sprue may comprise at least two movable parts. As disclosed in fig 12 a further extension of the length of the down sprue 35 in the extended state may be obtained when it comprise three parts (31 , 33, 34), which are telescopically movable in relation to each other.

The inventive holding plate 26 for the fixation of the inventive down sprue assembly 11 is shown in figure 9. It comprises at least one mounting opening 27, which via at least one channel 28 arranged in the holding plate 26 is adapted to be connected with the conduit 14 for providing pressurised air to the down sprue.

The holding plate is simply mounted at the lower side of the cope press plate 23. Modifications of the latter is avoided for the provision of the pressurised air to the down sprue.

Especially advantageously is when the holding plate 26 comprises at least two mounting openings 27 connected by channels 28 as depicted in figure 9. The openings 27 are closed off by airtight plugs 29 of which only one is depicted in figure 11 for the reason of clarity. After the holding plate 26 has been mounted to the cope press plate 23, the plug at the desired position is removed and the down sprue is mounted in the opening without plug. The remaining plugs 29 is left in the remaining mounting openings so that they are airtight when the pressurised air is present in the channels 28 of the holding plate and in the cavity 12 of the down sprue.

Low manufacturing costs are experienced when the channels are arranged as grooves 28 in the upper surface 32 of the holding plate 26 as depicted in figure 9. The grooves 28 are simply sealed off when the plate 26 is mounted to the cope press plate 23, for example by the upper surface of the holding plate being covered by a sealing layer 30, which could be of plastic material.

The pressure of the air in the channels 28 and in the cavity 12 of the down sprue 11 may advantageously be kept in the range of 0,1 - 10 bar available in most production facilities.

Claims

Patent Claims.

1. A method for the moulding of sand moulds (4, 5) in a moulding machine (1 ) having upper and lower moulding boxes (6, 7) and having a telescopic down sprue assembly (11 ) arranged in the upper moulding box (6) during moulding, comprising the steps of:

clamping a matchplate (19) with moulding pattern between upper and lower moulding boxes (6, 7),

activating the down sprue assembly (11) with pressurised air so that a telescopic extendable part (18) of the assembly (11 ) is forced on to the matchplate (19),

blowing sand (22) into the moulding boxes (6, 7),

squeezing the sand (22),

deactivating the pressurised air from the down sprue assembly (11 ),

withdrawing the upper and lower moulding boxes (6, 7) from each other thereafter removing the matchplate (19).

2. Method according to claim 1 , whereby the down sprue (11 ) is subsequently lifted up from the upper sand mould (6).

3. Method according to claim 1 , whereby the moulding boxes (6, 7) are closed and the sand moulds (4, 5) are subsequently removed through the bottom of the lower moulding box (7) before the down sprue (11 ) is lifted up from the upper sand mould (6).

4. Method according to claim 1 , whereby the pressurised air is kept within a pressure range of 0,1 - 10 bar.

5. A moulding machine (1 ) for the moulding of sand moulds (4, 5) by clamping a matchplate (19) with moulding pattern between upper and lower moulding boxes (6, 7), and having a telescopic down sprue assembly (11) arranged in the upper moulding box (6) during moulding, wherein

the telescopic down sprue assembly (11) has an inner cavity (12), which is connected with means (13-17) for providing pressurised air so that a pressure is created in the cavity (12).

6. Moulding machine according to claim 5, wherein the cavity (12) of the down sprue assembly (11) is adapted for providing an extension of the down sprue assembly (11) by the creation of the pressure.

7. Moulding machine according to claim 5, wherein the means for providing 0 pressurised air is adapted to keep the pressurised air in a pressure range between 0,1 - 10 bar.

8. Moulding machine according to claim 5, wherein the telescopic down sprue assembly (11 ) is fixed to an upper holding plate (26) arranged above 5 the upper moulding box (6).

9. Telescopic down sprue assembly 11 for moulding machine for the moulding of sand moulds (4, 5) by clamping a matchplate (19) with moulding pattern between upper and lower moulding boxes (6, 7), wherein o the upper part (31 ) of the telescopic down sprue assembly (11 ) has an inner cavity (12), the opening (25) to which is adapted to be connected with means (13-17) for providing pressurised air to the cavity (12) for building up internal pressure.

10. Telescopic down sprue assembly according to claim 9, wherein the cavity (12) is arranged in the upper part (31) of the telescopic down sprue assembly (11) and that the lower part (18) fits into the cavity (12) with slidable engagement, or vice versa.

11. Telescopic down sprue assembly according to claim 9, wherein the slidable engagement between the parts (18, 31 ) features a radial gap in the range of 0,01 - 0,50 mm.

12. Telescopic down sprue assembly according to claim 9, wherein the telescopic down sprue assembly (11 ) is free of any solid spring means.

13. Telescopic down sprue assembly according to claim 9, wherein the telescopic down sprue assembly (11 ; 35) comprises three parts (12, 18; 12, 33, 34), which are telescopically movable in relation to each other.

14. Holding plate 26 for telescopic down sprue assembly (11 ) used in moulding machine (1 ) for the moulding of sand moulds (4, 5) by clamping a matchplate (19) with moulding pattern between upper and lower moulding boxes (6, 7), wherein the holding plate (19) has at least one mounting opening (27) for the fixation of the telescopic down sprue assembly (11 ), which mounting opening (27) via at least one channel (28) arranged in the holding plate (26) is adapted to be connected with means for providing pressurised air.

15. Holding plate according to claim 14, wherein is arranged at least two mounting openings (27) connected by channels (28), and which openings (27) are closed off by airtight plugs (29).

i 16. Holding plate according to claim 14, wherein the channels are arranged as grooves (28) in the upper surface (32) of the holding plate (26).

17. Holding plate according to claim 14, wherein the upper surface (32) is essentially covered by a sealing layer (30).

18. Use of pressurised air for providing extension pressure in the cavity of a telescopic down sprue assembly used in moulding machine for the moulding of sand moulds by clamping a matchplate with moulding pattern between upper and lower moulding boxes.