Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1995-11-29
1998-05-26
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75 1035, 75690, 75693, 75382, 266 87, 266227, C22B 1302, C22B 2506
Patent
active
057558892
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for recovering solder from dross.
During soldering on an industrial scale, a heated solder bath is maintained and it is necessary to scrape off dross from the top of the solder bath at frequent intervals, the dross primarily being formed of oxides of tin and lead. However, up to 70% of the solder can be lost with the dross. Good solder can be reclaimed from the dross and conventionally this is done by simply heating the dross. However, this is a relatively inefficient method and barely economic.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a method of recovering solder from dross, the method comprising the steps of heating and compressing the dross.
It is understood that dross consists of pockets of good solder which are surrounded by a crust-like envelope of tin and lead oxides. In the present invention, when the dross is heated and compressed, the oxide crust bursts and liquid solder can escape. In addition, any free solder in the dross removed from the solder bath will also be recovered. It is expected that at least 60% and probably more than 75% of the solder in the dross will be recovered.
The dross may be heated first and subsequently compressed.
The dross is preferably heated to a temperature of at least substantially 225.degree. C. The dross may be heated to a temperature of substantially 350.degree. C. Higher temperatures may be used.
The dross may be compressed with a pressure of at least substantially 0.5 kg/cm.sup.2. The pressure may be substantially 5 kg/cm.sup.2. Other pressures of say 1 kg/cm.sup.2 to 7.5 kg/m.sup.2 may be used.
According to a second aspect of the present invention, there is provided apparatus for recovering solder from dross, the apparatus comprising:
a chamber for receiving dross;
a heater for heating dross in the chamber;
compression means for compressing the dross; and,
an outlet from the chamber through which recovered solder can pass.
The compression means may include a piston movable in the chamber to bear down on dross in the chamber.
A drain tray may be positioned at the outlet.
The drain tray may be provided with a plurality of apertures and may be positioned below the outlet to allow recovered solder to pass through the outlet through the drain tray apertures to a collection point. Means may be provided for reciprocatingly moving the drain tray sideways.
The heater may consist of an electric heater around the chamber.
Means may be provided for monitoring the temperature inside the chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
An example of the present invention will be described with reference to the accompanying drawings, in which:
FIG. 1 is a perspective view of a first example of apparatus according to and for carrying out the present invention;
FIGS. 2a-2f are schematic diagrams showing the steps involved in the method of the present invention; and,
FIG. 3 is a partially sectioned elevation of a second example of apparatus according to and for carrying out the present invention.
DESCRIPTION OF THE INVENTION
The first example of apparatus shown in FIGS. 1 and 2 has a hollow cylindrical chamber 1. The chamber 1 is vertically disposed and is open at the top end 2 and at the bottom end 3. An inlet 4 is provided in the side wall 5 of the chamber 1. A chute or hopper 6 is fixed to the side wall 5 of the chamber 1 at the inlet 4 so that dross can be fed through the hopper 6 into the interior of the chamber 1. Electric heating elements (not shown) may be provided at the base of the hopper 6. A plurality of electric heating elements 8 encircle the chamber 1.
The chamber 1 is mounted is fixed to a generally rectangular frame 10. A cast iron drain tray or grille 12 is positioned below the supporting bottom plate 9 and can slide back and forth below the chamber 1 in grooves provided in opposed side walls 15, 16 of the frame 10. The grille 12 has an array of apertures 13 drilled in one end and also has a through-hole 11 at the other
REFERENCES:
patent: 2278135 (1942-03-01), Osborn
patent: 4119136 (1978-10-01), Gancarz, Jr.
patent: 4334664 (1982-06-01), Gancarz, Sr.
patent: 4540163 (1985-09-01), van Linden et al.
patent: 4565572 (1986-01-01), van Linden et al.
patent: 4575392 (1986-03-01), Julliard et al.
patent: 4772320 (1988-09-01), van Linden et al.
Andrews Melvyn
Apple House Elecronics Ltd.
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