GB1600389A - Mould caps - Google Patents

Description

(54) IMPROVEMENTS RELATING TO MOULD CAPS (71) We, PONTARDAWE FOUND RY & ENGINEERING CO., LIMITED, a British Company of Pontardawe, Swansea, West Glamorgan, do hereby declare the invention for which we pray that a Patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention is concerned with improvements relating to mould caps of the kind (hereinafter referred to as- being of the kind specified) used in conjunction with "bottletop" moulds in the casting of ingots of metal, such moulds having an interior cavity and a neck (afforded by a spigot hole of the mould) extending to the interior cavity. The cavity is open at the bottom, and in use the mould is placed on a flat base. and molten metal (e.g. steel) is introduced into the cavity through the spigot hole, the molten metal filling the cavity and at least partially filling the spigot hole. The mould cap has a tapered peripheral surface, and is inserted into the spigot hole, a first interior portion of the cap being positioned within the spigot hole, and a second, exterior portion of the cap seating against the upper edge of the mould bounding the spigot hole, and the molten metal in the mould is allowed to cool.

To allow the solidfied ingot to be readily removed from the mould, both the cavity and the spigot hole are tapered, increasing in cross-sectional area in a direction extending towards the bottom of the mould. In order that the molten metal in the spigot hole, in the space between the neck of the mould and the mould cap, cools as quickly as possible, it is preferred that the size of this space, and in particular the angle included between the tapered spigot hole and the peripheral surface of the mould cap, be kept as small as possible, and typically, the angle of taper of the spigot hole is about 5 to 10 to the vertical.

Since the angle of taper of the spigot hole itself is determined by the necessity to obtain good extraction of the ingot, the size of this space can only be reduced by using a mould cap in the form of a frustrume, having a relatively small taper angle, (e.g., 10 to the vertical). The seal between the mould and the cap would thus be produced by the line of contact between the peripheral surface of the frustrume and the upper edge of the mould bounding the spigot hole.

Ideally, the upper edge of the mould is as a sharp edge of fixed diameter, to ensure a good seal between said upper edge and the spigot cap. if a good seal is not obtained, a molten metal can be sprayed from the mould, and loss in internal pressure results in a deterioration in the "rimming" of the molten metal on solidification. In use, the spigot hole wears, particularly in the vicinity of said upper edge, both as a result of the insertion of the cap into the spigot hole, and due to the eroding action of the molten metal poured into the mould. This produces a deterioration in the quality of seal between the cap and the upper edge, and leakage may occur from the spigot hole, which may cause the mould cap to stick in the neck of the mould, producing further wear at said upper edge when the cap is eventually removed.

Conversely, mould caps could be used in the form of a frustrume having a relatively large taper angle (e.g. 30 to the vertical) sufficient to ensure a good seal between the neck of the mould, despite some erosion of the spigot hole having taken place.

However, such a larger taper angle, together with the existing taper of the spigot hole itself, would result in an increase in the space between the neck of the mould and the mould cap, increasing the time taken for solidification of the metal in the neck of the mould.

It is conventional practice therefore to use mould caps having a taper angle somewhat between the small and large angles above described, such caps producing some problems of seal when the top edge of the mould becomes eroded, and a somewhat increased time for solidification of the molten material in the spigot hole adjacent to the cap.

Typically the taper angle of a conventional mould cap is 20 to the vertical.

According to this invention there is provided a mould cap of the kind specified, in which the angle of taper of the peripheral surface of the first portion thereof is smaller than the angle of taper of a second portion thereof.

For example, the peripheral surface may be provided with a double taper, the two portions for example, being separate identifiable portions of a double frustrume.

Thus, the angle of taper of the first said portion may be selected to satisfy the requirements of the first portion alone including the desirability of minimising the space between the spigot hole and the cap, to increase chilling of the molten metal in this space, and the taper angle of the second said portion may be selected to satisfy the requirements of the second portion along, including the desirability of providing effective sealing with the edge of the mould bounding the spigot hole.

Thus, the taper angle of the first said portion may be less than the taper angle of conventional moulds caps, for example lying between 0 and 20 to the vertical, and the angle of taper of the second portion may be greater than the taper angle of conventional mould caps, for example, lying between 20 and 45" to the vertical.

Desirably, however, to enable convenient positioning of the cap into the spigot hole, the taper angle of the first said portion is between 10 and 20 to the vertical (preferably about 15 ) and the taper angle of the said second portion is between 25 and 40 to the vertical (preferably about 30 ).

However, it is within the scope of this invention for the taper angle of the first said portion to be generally similar to the taper angle of a conventional mould cap, and the taper angle of the second said portion to be greater than this.

Alternatively, the peripheral surface may be formed as a continuous curved surface, for example as may be formed by revolution about a longitudinal axis of the mould cap, of a curved line such as part of a circle, parabola or hyperbola. In such circumstances, the tangent to the peripheral surface of the mould cap will vary, desirably being between 0 and 20 to a line parallel to the longitudinal axis of the mould cap, at an interior portion of the mould cap, and between 20 and 45" to a line parallel with a longitudinal axis of the mould cap at an exterior portion of the mould cap.

There will now be given a detailed description, to be read with reference to the drawings accompanying the provisional specification, of a mould cap which is a preferred embodiment of this invention, and which has been selected to illustrate this invention by way of example.

In the drawings accompanying the provisional specification: Figure I is a schematic sectional view of an upper portion of a "bottle-top" ingot mould, when relatively new; Figure 2 is a view similar to that shown in Figure 1, illustrating wear having taken place around the top edge of the spigot hole thereof; Figure 3 is a schematic view of a conventional type of mould cap.

Figure 4 is a side elevation, part in section, of the mould cap which is the preferred embodiment of this invention; Figure 5 is a plan view on Figure 4; Figure 6 is a view illustrating the mould cap which is the preferred embodiment of this invention, in position within the spigot hole of an ingot mould; and Figure 7 is a view illustrating an alternative form of taper which may be employed; Figure 1 illustrates an upper part of a conventional "bottle-top" ingot mould, having a mould cavity 6, generally in the form of a bottle, and a spigot hole 8, through which molten metal (e.g. steel) is poured into the mould cavity 6. In use, the mould may be clamped against a bottom plate, and after solidification of the metal within the mould cavity and spigot hole, the mould and bottom plate will be separated, and a metal ingot, in the form of a bottle, will be removed from the mould cavity.

In order to obtain ready separation of solidified metal from the spigot hole 8, the sides of the spigot holes are tapered, increasing in diameter towards the interior of the mould, as shown in Figure 1.

When the mould is new, the top edge 11 between the peripheral surface of the spigot hole 8 and the top surface 10 of the mould will be sharp.

A conventional mould cap is shown in Figure 3, and is generally in the form of a frustrume, havinga taper angle of about 20 , and in use, after the cavity has been filled with molten metal, the mould cap will be dropped into the spigot hole, engaging with the top edge 11 to close the cavity, allowing the molten metal to solidify under a small internal pressure.

In use, the continued insertion of the conventional mould cap into the spigot hole, and repeated pouring of molten metal into the cavity through the spigot hole will cause the top edge 11 to become eroded, as is shown in Figure 2. Thus, a deterioration in the seal obtained between the mould cap and the top edge results, which allows a small amount of leakage of molten metal and/or gasses from the mould. This increases the deterioration of the top edge, and also tends to cause the mould cap to stick to the mould itself, tending to break small pieces of the mould away when the mould cap is hammered free.

The mould cap which is the preferred embodiment of this invention (Figure 4 and 5) is in the form of a double frustrume, that is having a peripheral surface provided with a double taper. The taper angle of a first, lower portion 20a of the mould cap (being that portion which, in the use of the mould cap will be located within the spigot hole 8 of the mould) is about 15 to the vertical, but may be varied to meet individual requirements. The taper angle of a second, upper portion 20b of the mould cap (being that portion which in the use of the mould cap will seat against the top edge 11 of the mould) is about 30 to the vertical, but similarly may be varied to suit individual requirements.

In this manner. when the mould cap 20 is placed within the spigot hole 8 of the mould, the surface of the portion 20b, seats against and provides a good seal in conjunction with the top edge 11, despite the top edge 11 having been eroded somewhat. Additionally, in view of the smaller taper angle of the portion 20a, the dimensions X between the neck of the mould and the mould cap is relatively small, obtaining a greater chill of the molten metal (steel) previously poured into the mould cavity.

Whereas in the preferred embodiment illustrated in Figure 4 and 5, the two portions 20a and 20b are separately identifiable portions of a double frustrume, the two parts may be provided by portions of a continuous curved surface, as may be formed by revolution about a longitudinal axis of a parabola or hyperbola. Such a construction is shown in Figure 7, in which the taper angle of the peripheral surface of the mould cap varies between an angle of about 30 , in the vicinity of the point of contact of the mould cap with the top edge of the mould, to about 15"at a terminal position of the peripheral surface within the spigot hole.

WHAT WE CLAIM IS: 1. A mould dap of the kind specified, in which the angle of taper of the peripheral surface of the first portion thereof is smaller than the angle of taper of the peripheral surface of the second portion thereof.

2. A mould cap according to claim 1 wherein the peripheral surface is provided with a double taper, the two portions being separate identifiable portions of a double frustrume.

3. A mould cap according to one of claims 1 and 2 wherein the angle of taper of the first portion is between 0 and 20 .

4. A mould cap according to claim 3 wherein said angle is between 10 and 20 .

5. A mould cap according to claim 4 wherein said angle is about 15".

6. A mould cap according to any one of the preceding claims wherein the angle of taper of the second portion is between 20 and 45".

7. A mould cap according to claim 6 wherein said angle is between 25 and 40 .

8. A mould cap according to claim 6 wherein said angle is about 30".

9. A mould cap according to claim 1 wherein the peripheral surface is formed as a continuous curved surface, the tangent to the peripheral surface of said mould cap varying between 0 and 20 to a line parallel with the longitudinal axis of the mould cap at an interior portion of the mould cap, and between 20 and 45" to a line parallel with the longitudinal axis of the mould cap at an exterior portion of the mould cap.

10. A mould cap according to claim 9 wherein the peripheral surface is formed by revolution of a curved line about a longitudinal axis of the mould cap.

11. A mould cap constructed and arranged substantially as hereinbefore described with reference (a) to Figures 4, 5, and 6, or (b) to Figures 7 of the drawings accompanying the provisional specification.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. shown in Figure 2. Thus, a deterioration in the seal obtained between the mould cap and the top edge results, which allows a small amount of leakage of molten metal and/or gasses from the mould. This increases the deterioration of the top edge, and also tends to cause the mould cap to stick to the mould itself, tending to break small pieces of the mould away when the mould cap is hammered free. The mould cap which is the preferred embodiment of this invention (Figure 4 and 5) is in the form of a double frustrume, that is having a peripheral surface provided with a double taper. The taper angle of a first, lower portion 20a of the mould cap (being that portion which, in the use of the mould cap will be located within the spigot hole 8 of the mould) is about 15 to the vertical, but may be varied to meet individual requirements. The taper angle of a second, upper portion 20b of the mould cap (being that portion which in the use of the mould cap will seat against the top edge 11 of the mould) is about 30 to the vertical, but similarly may be varied to suit individual requirements. In this manner. when the mould cap 20 is placed within the spigot hole 8 of the mould, the surface of the portion 20b, seats against and provides a good seal in conjunction with the top edge 11, despite the top edge 11 having been eroded somewhat. Additionally, in view of the smaller taper angle of the portion 20a, the dimensions X between the neck of the mould and the mould cap is relatively small, obtaining a greater chill of the molten metal (steel) previously poured into the mould cavity. Whereas in the preferred embodiment illustrated in Figure 4 and 5, the two portions 20a and 20b are separately identifiable portions of a double frustrume, the two parts may be provided by portions of a continuous curved surface, as may be formed by revolution about a longitudinal axis of a parabola or hyperbola. Such a construction is shown in Figure 7, in which the taper angle of the peripheral surface of the mould cap varies between an angle of about 30 , in the vicinity of the point of contact of the mould cap with the top edge of the mould, to about 15"at a terminal position of the peripheral surface within the spigot hole. WHAT WE CLAIM IS:

1. A mould dap of the kind specified, in which the angle of taper of the peripheral surface of the first portion thereof is smaller than the angle of taper of the peripheral surface of the second portion thereof.

2. A mould cap according to claim 1 wherein the peripheral surface is provided with a double taper, the two portions being separate identifiable portions of a double frustrume.

3. A mould cap according to one of claims 1 and 2 wherein the angle of taper of the first portion is between 0 and 20 .

4. A mould cap according to claim 3 wherein said angle is between 10 and 20 .

5. A mould cap according to claim 4 wherein said angle is about 15".

6. A mould cap according to any one of the preceding claims wherein the angle of taper of the second portion is between 20 and 45".

7. A mould cap according to claim 6 wherein said angle is between 25 and 40 .

8. A mould cap according to claim 6 wherein said angle is about 30".

9. A mould cap according to claim 1 wherein the peripheral surface is formed as a continuous curved surface, the tangent to the peripheral surface of said mould cap varying between 0 and 20 to a line parallel with the longitudinal axis of the mould cap at an interior portion of the mould cap, and between 20 and 45" to a line parallel with the longitudinal axis of the mould cap at an exterior portion of the mould cap.

10. A mould cap according to claim 9 wherein the peripheral surface is formed by revolution of a curved line about a longitudinal axis of the mould cap.

11. A mould cap constructed and arranged substantially as hereinbefore described with reference (a) to Figures 4, 5, and 6, or (b) to Figures 7 of the drawings accompanying the provisional specification.