GB2312388A

GB2312388A - Molten metal pouring apparatus

Info

Publication number: GB2312388A
Application number: GB9608584A
Authority: GB
Inventors: Richard Peter Grenfell
Original assignee: PARADAY FABRICATIONS Ltd
Current assignee: PARADAY FABRICATIONS Ltd
Priority date: 1996-04-24
Filing date: 1996-04-24
Publication date: 1997-10-29
Anticipated expiration: 2016-04-24
Also published as: GB9608584D0; GB2312388B

Abstract

Molten metal pouring apparatus 10 has a bath 12 in which molten metal may be contained prior to being poured. A valve controls an outlet at 16, from which metal may pour into a mouth 40 of a mould 42. A hydraulic or pneumatic cylinder 32 allows the bath 12 to be tilted to maintain a constant ferrostatic head over the outlet 16. The support arrangement also causes the outlet 16 to undergo translational movement as it tilts, to compensate for the re-direction caused by the tilting, so that the molten metal is still delivered reliably to the same point in the mouth 40, regardless of the orientation of the bath 12. The support means may be operable to raise and lower the rearward region of the bath.

Description

Pouring Molten Metal The present invention relates to pouring molten metal.

Various foundry operations require amounts of metal to be poured repeatedly and precisely, for instance to fill a series of identical moulds with equal amounts of molten metal for casting. In some foundries, "bottom pour" units are used. These consist of an insulated bath in which molten metal is housed, and a valve allowing molten metal to pour from the bath into moulds beneath. This arrangement is relatively cheap, but suffers the disadvantage that as the bath empties, the flow characteristics of the metal flowing through the valve can change s'ignificantly, including changing between lamina and nonlamina flow, so that the point to which the metal is ultimately dispensed (and at which the mould mouth must be located) can vary significantly and somewhat unpredictably. Although commonly used, this problem makes the arrangement undesirable on safety grounds.

A more complex arrangement uses a pressurised vessel to force molten metal from a main container through a relatively narrow pipe to a secondary container from which it is dispensed. Varying the pressure in the main chamber allows the head in the secondary chamber to be maintained constant.

This improves the flow characteristics at the outlet valve, but requires sophisticated and expensive control arrangements and a more elaborate and expensive arrangement of baths. Moreover, runnings costs are much higher, because the arrangement, particularly the connecting pipes, must be kept heated at all times to avoid metal freezing and blocking the pipes. A typical unit with five tonne capacity may suffer heat loss of 90kW constantly, even when well insulated.

The present invention seeks to provide an improved arrangement without introducing unacceptable complexity.

The present invention provides molten metal pouring apparatus, comprising bath means in which molten metal may be contained prior to being poured, valve means selectively operable to allow molten metal to pour from the bath means through an outlet, and support means which support the bath means during use and are operable to re-orient the bath means to maintain a substantially constant head of molten metal at the valve means while the bath means is emptied.

The support means are preferably operable to tilt the bath means. The bath preferably has a generally forward region in which the valve means is located, and a generally rearward region, the support means being operable to tilt the bath means to vary the relative heights of the forward and rearward regions. The support means may be operable to raise and lower the rearward region. The bath means may be relatively large in the rearward region, for bulk storage of molten metal, and have a relative narrow forward portion.

The outlet is preferably carried by the bath means and is re-oriented therewith. The support means may be operable to move the outlet as the outlet is re-oriented, the degree of movement being selected to substantially compensate for variation in the flow characteristics of molten metal leaving the outlet, whereby to cause molten metal to be poured to a position which is substantially independent of the orientation of the bath means and outlet. The support means are preferably arranged to provide for translational movement of the outlet as the bath means is re-oriented. The support means may comprise at least one member, such as roller means, which, in use, is movable along a track as the bath means is re-oriented, to provide translational movement from the re-orientation. The support means may comprise guide means and a member constrained by the guide means to travel along a predetermined path to cause re-orientation of the bath means to produce translational movement in a predetermined relationship. The guide means may comprise at least one guide surface carried by the bath means or support means, and a member as aforesaid carried by the other of the bath means and support means.

Control means are preferably provided to monitor the head of molten metal at the valve and to re-orient the bath means to maintain a substantially constant head as aforesaid. The support means may comprise a fluid-actuated piston and cylinder arrangement operable to re-orient the bath means. The support means may be operable to re-orient the bath means to cause molten metal to flow away from the valve means while pouring is interrupted. The support means may re-orient the bath means sufficiently to empty the bath means without pouring through the valve means.

One embodiment of the present invention will now be described in more detail, by way of example only, and with reference to the accompanying drawings in which: Figs. lA, 1B, 1C are schematic elevations of apparatus according to the invention, indicating three extreme positions available; Fig. 2A is a schematic plan view of the bath alone; Fig. 2B is a vertical section at the line 2-2 in Fig. 2A; and Figs. 3A and 3B are schematic diagrams illustrating pouring trajectories of molten metal leaving the apparatus of Fig. 1.

Figs. 1A, 1B and 1C show molten metal pouring apparatus indicated generally at 10 and comprising a bath 12 in which molten metal may be contained prior to being poured. A valve 14 (Fig. 3A) is selectively operable to allow molten metal to pour from the bath through an outlet at 16. Support means indicated generally at 18 support the bath 12 during use and can reorient the bath, as indicated in the drawing and to be described in more detail later, to maintain a substantially constant head of molten metal (ferrostatic head) at the valve 14 while the bath 12 is emptied.

In more detail, the bath 12 is an insulated container for holding molten metal prior to pouring, and has a relatively large rearward end 20A and a relatively narrow forward neck 20B (see Fig. 2). The outlet 16 controlled by the valve 14 is located in the neck 20B. The rear end 20A allows the capacity of the bath to be adequately high, a typical capacity being one to two tonnes.

The valve 14 is shown in more detail in Fig. 3A. A stopper 22 can be raised or lowered by a drive mechanism 24 (Fig. 1) to stop or open the outlet 16.

The diameter of the outlet 16 may typically be about 20mm and the valve would typically be used to control pouring to allow between about 15-30kg of molten metal to pour before stopping the outlet 16.

The neck 20B is supported by cylindrical rollers 26 which project to either side of the neck 20B and rest on rails 28. The rails 28 form part of a frame 30. The rear end 20A is supported by a hydraulic cylinder 32 acting between the end 20A and the frame 30. Extending and retracting the cylinder 32, under appropriate hydraulic control, causes the rear 20A to rise from a lowermost position (Fig. 1B) through intermediate positions (not shown) to an uppermost position (Fig. 1A). This raises and lowers the rear end 20A relative to the neck 20B, which remains at substantially the same height set by the position of the rails 28. Accordingly, as the rear end 20A is raised, more molten metal will flow from the main body into the neck 20B and conversely, molten metal can be encouraged to flow back from the neck 20B into the main body 20A by lowering the rear end 20A.

In consequence, the level of molten metal in the vicinity of the valve 14 can be controlled by actuation of the cylinder 32. The ferrostatic head at the valve can therefore be controlled, so that flow characteristics remain substantially constant. It is preferable to maintain a relatively small ferrostatic head, so that lamina flow is maintained through the valve. This makes pouring more predictable, the significance of which will be described in more detail below.

It can be seen from Figs. 1A and 1B that as the rear end 20A rises and falls, the rollers 26 will roll along the rails 28, thereby converting the re orientation of the bath into translational movement of the outlet 16. This movement is intended to compensate for the rotation of the outlet 16 which would in turn cause the ultimate point of delivery of molten metal to move. If necessary, this translation can be further constrained by a guide arrangement such as that indicated at 36 which consists of short projections 36A from either side of the bath 12 and running in guide channels 36B shaped to cause a predetermined translational movement of the outlet 16 in response to changes in height of the rear end 20A.

The significance of the translational movement can now be described by considering Fig. 3 in more detail.

In Fig. 3A, the outlet 16 is vertically aligned at the vertical axis 40A of the mouth 40, to produce a vertical stream 38A of molten metal. Since flow characteristics through the valve 14 have been kept lamina, the stream 38A will be predictable and substantially vertical, so that the mouth 40 of a mould 42 can be placed directly beneath the outlet 16.

If the rear end 20A of the bath is moved up to maintain the head as the bath empties, the neck 20B will roll forward so that in addition to tilting, the outlet 16 will move forward to a position indicated in Fig. 3B. At this position, molten metal will still exhibit lamina flow and produce a stream 38B which is predictably parabolic, or substantially so. Thus, by ensuring appropriate translational movement forward, the nozzle will still deliver molten metal to the same point, so that the mouth 40 is not required to move. It is to be noted that in Fig. 3B, the central axis 16A of the outlet 16 is tilted and does not intersect the axis 40A within the mouth 40, by virtue of the forward movement.

Similarly, if the rear end 28 is dropped (to a position it will occupy when the bath is first filled) the outlet 16 will tilt in the opposite direction and also move backwards by virtue of the neck 20B rolling back along the rails 28. The outlet 16 will then adopt a position which mirrors the position in Fig. 3B, but to the other side of the vertical axis of the mouth 40. Again, flow can be kept lamina so that the stream will again be predictably parabolic, or substantially so, and molten metal will again be delivered accurately to the mouth 40 without requiring the mould 42 to be moved.

Thus, tilting the bath not only maintains a substantially constant ferrostatic head, so that flow characteristics are predictable, but also creates an appropriate translational movement to deliver molten metal to the same point regardless of tilt. The precise relationship between the position of the outlet 16 and the inclination of the bath 12 will depend on a number of factors, including the ferrostatic head being maintained, the valve and outlet dimensions, the vertical spacing between the outlet and the mould mouth, and the nature of the material being poured, but it is not envisaged that the skilled man would experience any difficulty in applying the principles disclosed here in any particular application.

Fig. 1C shows the bath 12 tipped right back to a position 50 in which the rollers 26 have left the rails 28 and the bath is tipped back through approximately 900. This position allows the bath to be emptied and is achieved by using the hydraulic cylinder 32. Consequently, if pouring is interrupted, the bath can be emptied so that any danger of metal freezing in the bath or valve is removed, but the bath does not require heating. This results in a significant cost saving. Heating, such as inductive heating, could be applied to the bath if desired.

A further advantage of maintaining a substantially constant ferrostatic head, preferably a small head to produce lamina flow, is that valve design can be simplified with consequent cost saving and reliability.

In practice, it will be desirable to provide an automatic arrangement for adjusting the tilt to maintain the desired ferrostatic head, such as by providing a sensor in the vicinity of the valve 14, the output from which controls the degree of extension of the cylinder 32. The sensor could be based as a float in the molten metal, and an arrangement (such as limit switches) to detect the float position.

Many variations and modifications can be made to the apparatus described above without departing from the scope of the present invention. In particular, many other arrangements for supporting the bath could be envisaged and other valve, bath and outlet designs could be used. Motive power for re-orienting the bath could be provided in other ways, and other arrangements could be used for controlling translational movement of the outlet 16.

A further advantage of the arrangement is that if pouring is temporarily suspended, the bath can be tilted back to draw molten metal away from the valve and outlet, avoiding freezing.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

Claims:-

1. Molten metal pouring apparatus, comprising bath means in which molten metal may be contained prior to being poured, valve means selectively operable to allow molten metal to pour from the bath means through an outlet, and support means which support the bath means during use and are operable to re-orient the bath means to maintain a substantially constant head of molten metal at the valve means while the bath means is emptied.

2. Apparatus according to claim 1, in which the support means are operable to tilt the bath means.

3. Apparatus according to claim 1 or 2, in which the bath means has a generally forward region in which the valve means is located, and a generally rearward region, the support means being operable to tilt the bath means to vary the relative heights of the forward and rearward regions.

4. Apparatus according to claim 3, in which the support means are operable to raise and lower the rearward region.

5. Apparatus according to claim 3 or 4, in which the bath means is relatively large in the rearward region, for bulk storage of molten metal, and has a relative narrow forward portion.

6. Apparatus according to any preceding claim, in which the outlet is carried by the bath means and is re-oriented therewith.

7. Apparatus according to any preceding claim, in which the support means are operable to move the outlet as the outlet is re-oriented, the degree of movement being selected to substantially compensate for variation in the flow characteristics of molten metal leaving the outlet, whereby to cause molten metal to be poured to a position which is substantially independent of the orientation of the bath means and outlet.

8. Apparatus according to any preceding claim, in which the support means are arranged to provide for translational movement of the outlet as the bath means is re-oriented.

9. Apparatus according to claim 8, in which the support means comprise at least one member which, in use, is movable along a track as the bath means is re-oriented, to provide translational movement from the re-orientation.

10. Apparatus according to claim 9, in which the member is a roller means.

11. Apparatus according to any of claims 8, 9 and 10, in which the support means comprise guide means and a member constrained by the guide means to travel along a predetermined path to cause re-orientation of the bath means to produce translational movement in a predetermined relationship.

12. Apparatus according to claim 11, in which the guide means comprise at least one guide surface carried by the bath means or support means, and a member as aforesaid carried by the other of the bath means and support means.

13. Apparatus according to any preceding claim, in which control means are provided to monitor the head of molten metal at the valve and to re-orient the bath means to maintain a substantially constant head as aforesaid.

14. Apparatus according to any preceding claim, in which the support means comprise a fluid-actuated piston and cylinder arrangement operable to re-orient the bath means.

15. Apparatus according to any preceding claim, in which the support means are operable to re-orient the bath means to cause molten metal to flow away from the valve means while pouring is interrupted.

16. Apparatus according to any preceding claim, in which the support means can re-orient the bath means sufficiently to empty the bath means without pouring through the valve means.

17. Molten metal pouring apparatus substantially as described above, with reference to the accompanying drawings.

18. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.