GB2257383A - Duct for conveying molten metal - Google Patents

Abstract

A section of a molten-metal-conveying duct such as a launder comprises a dovetailed end 9 for engagement with a complementary dovetailed end 10 on another section of a molten-metal-conveying duct. <IMAGE>

Description

DUCT FOR CONVEYING MOLTEN METAL This invention relates to ducts for conveying molten metal and is particularly, though not exclusively, to launders.

Launders are used in foundries for conveying metal from a crucible to a mould. They comprise a generally U-section channel, a lid optionally covering the mouth of the U in use.

As launders are long (e.g. 3 metres) they are usually made in sections which are lap-jointed together (i.e. an end of one section lying within an end of the neighbouring section). The sections themselves lie within a channel and are supported within the channel by refractory material. At one or both ends of the channel ceramic fibre wadding is used to accommodate movement due to thermal expansion and contraction in use.

To prevent metal solidifying in the launder and to ensure full drying-out of the launder, launders are usually preheated. Pre-heating naturally results in thermal expansion of the launder sections and lap-jointing allows relative movement of the sections and the use of refractory fibre at the ends of the sections accommodate movement so preventing the launder sections arching out of the surrounding channel when preheated.

When, however, the launder is removed from its preheating furnace and positioned ready for use naturally there will be some cooling and this results in thermal contraction.

As lap-joints allow some degree of relative movement between the sections paths for escape of metal may result at the joints.

It has been proposed to overcome this problem by providing a joint as shown in Figure 1 in which a protrusion in one member of the lap-joint engages a groove in the other member of a lap-joint. This construction has several disadvantages a major one being manufacture to the tolerances required. The effect of this joint is to lock the two joined sections into engagement and it is found that when using this construction it is necessary to use more sections for a given length of launder than when using a simple lap-joint. The present Applicants have concluded that to obtain a joint for molten-metal conveying ducts such as launders it is advantageous to provide the joint in the form of a dovetailed joint.

The invention is illustrated by way of example in the drawings in which: Figure 1 is a part section of a prior art launder joint; and Figure 2 is a perspective view of a joint in accordance with the invention.

Discussing first the prior art design of Figure 1, this comprises a pair of launder sections 1, 2 the launder sections having reduced cross-section portions 3 and 4 respectively forming a lap-joint as is widely used. In this prior art construction a bead 5 on portion 3 engages with a complementary groove 6 on the part 4.

In the joint of the present invention launder sections 7 and 8 have respectively male 9 and female 10 dovetailed ends which inter-engage. This construction is easier to make than the prior art construction of Figure 1 and overcomes the disadvantages of the widely used lap-joints.

Claims (1)

1. A section of a molten-metal-conveying duct such as a launder, the section having a dovetailed end for engagement with a complementary dovetailed end on another section of a molten-metal-conveying duct.