GB2130699A

GB2130699A - Means for drying and/or storing welding powder or equivalent

Info

Publication number: GB2130699A
Application number: GB08330353A
Authority: GB
Inventors: Kai Lennart Neuvonen
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-11-19
Filing date: 1983-11-14
Publication date: 1984-06-06
Also published as: SE8305929L; GB2130699B; FI823989A0; IT8368190A0; NO154738C; DK528383A; FI73309C; DK528383D0; FI73309B; FR2536515A1; JPS59100387A; FI823989L; DE3304269A1; IT1171048B; NO834252L; GB8330353D0; NO154738B; SE8305929D0

Abstract

A means for drying and/or storing welding powder or equivalent, comprising a silo (1) with heating means (2), the purpose being to provide a drying and/or storing means which is in particular more efficient than those of prior art. As taught by the invention, the means includes a mixer (3), such as a conveyor, for mixing the powder during the drying process. The mixer consists advantageously of a conveyor, such as a screw conveyor, which has been disposed to transport powder from the lower part to the upper part of the silo. <IMAGE>

Description

SPECIFICATION Means for drying and/or storing welding powder or equivalent The present invention concerns a means for drying and/or storing welding powder or equivalent, comprising a silo with heating means.

Storing of welding powder in dry condition, and its drying, is a prerequisite for high quality welding. The drying of welding powder and its storing in humid work site conditions poses a difficult problem, which one has tried to solve e.g.

by the powder silos of prior art which are provided with a heating means for raising the temperature of the silo up to 3000C. In powder silos of prior art the heating means, that is an electric resistance, has been placed within the silo, e.g. on the bottom and/or in part on the walls. Furthermore, powder silos of prior art are provided with a filling aperture for adding powder to the silo and with a draining aperture usually placed on the bottom of the silo, with closing means, for withdrawing powder from the silo.

Powder silos of prior art are embarrassed by the drawback of inefficiency and, in particular, of slow and non-uniform spreading of heat within the silo.

The welding powder, which has a sand-like consistency and is a comparatively heavy and densely packing powder, efficiently prevents the rapid and uniform spreading of heat throughout the powder quantity that has been placed in the silo. The silos in present use have a comparatively large capacity, for instance more than 100 kg, whereby the heating of the whole powder quantity contained in the silo e.g. to 3000C with the heater commonly used, powered e.g. with 2 kW, takes quite long; on the whole, uniform temperature distribution is not achieved at all in powder silos in present use.

Recent investigations have shown that complete drying of the welding powder, which is a quite hygroscopic powder, implies that the powder should be heated up to 4500C, or even to 5000C. Powder silos of prior art are not suitable as regards their construction and their structural principles to be heated up to the said temperature level, which has become important in practice.

The object of the present invention is to eliminate the drawback mentioned. In particular, it is an object of the invention to provide a means for drying and/or storing welding powder which is appropriate for completely drying the welding powder and drying-heating it up to the level of 450#5000 C. Furthermore, it is an object of the invention to provide a powder silo which is substantially more powerful as to its drying capacity than any powder silo of prior art yet at the same time smaller in size. It is a further object of the invention to provide a means for drying and/or heating welding powder in which the heat is uniformly distributed all over the silo and in which uniform temperature distribution is achieved rapidly and efficiently.

Regarding the circumstances which are characteristic of the invention, reference is made to the accompanying claims.

The invention is based on a special conveyor which has been disposed to transport the powder in question from the lower part to the upper part of the silo. The said conveyor may be carried out in the form of any powder conveyor - particularly advantageous is a screw, helical or equivalent conveyor, placed for instance in a tubular conveying element and the heating means disposed in conjunction with the conveying element, e.g. in the shell of the tubular conveying element.

Thanks to the invention, the powder to be dried is efficiently mixed during the drying process.

Thereby the temperature distribution in the powder will be uniform and the heat spreads by effect of the mixing rapidly and efficiently to all parts of the material quantity that is being mixed.

When a powerful enough heater is used, the entire powder quantity to be dried and/or stored can be raised to the desired, high enough temperature, up to 450#500OC. Thanks to the conveyor or mixer, rapid spreading of heat into the powder to be dried and/or stored is achieved, whereby the drying capacity per unit time of the means increases substantially from what it was heretofore. It is thereby possible to use welding powder drying and/or storing means substantially smaller in size and smaller than those of prior art.

The invention is described in detail in the following with the aid of an embodiment example, with reference being made to the attached drawings, wherein:~ Fig. 1 presents, in elevational view and partly sectioned, a means according to the invention, and Fig. 2 presents in top view the same means as Fig. 1.

In Fig. 1 is seen a means according to the invention for drying and/or storing welding powder or equivalent. The means comprises a silo 1 provided with a heating means 2. The silo 1 is confined by side walls and a top and bottom wall.

On the silo, in its top wall, has been provided a filling aperture 12 for transferring powder into the silo, and a draining aperture 13 with closing members for withdrawing powder from the silo.

As taught by the invention, the silo 1 is provided with a particular mixer, that is a conveyor 3 for mixing the powder, in the embodiment of the figure for transporting the powder from the lower part to the upper part of the silo 1. In the embodiment depicted in Figs. 1 and 2, the conveyor 3 consists of a helical or screw conveyor, which has been placed within a tubular conveying element 4. The heating means 2 has in the embodiment depicted been disposed in conjunction with said conveying element 4, in the shell of the conveying element 4. In Fig. 1 there belongs to the conveying element a particular tubular inner shell 5 and a likewise tubular outer shell 6, these two defining between themselves a cylindrical interspace 7, in which the electric heating coil constituting the heating means 2 has been placed.The screw conveyor 3 has been placed inside the tube constituting the inner shell 5. The conveying element 4 has been placed inside the downwardly conically tapering silo 1 substantially vertically, spaced from the silo bottom and likewise spaced from the top wall of the silo. The screw conveyor 3 has been placed inside the conveying element 4 so that it extends substantially from the bottom of the silo substantially to the top wall of the silo. When the screw conveyor 3 is placed in rotation, the powder which has by gravity action settled on the bottom of the silo comes into contact with the screw conveyor extending down to the bottom which begins to transport powder into the conveying element and further inside the conveying element upward from the bottom to the upper part of the silo.On reaching the upper end of the conveying element, where the inner shell 5 and outer shell 6 of the conveying element have been interconnected by a particular flange 9 to prevent access of powder into the interspace 7, the powder runs to the outside of the conveying element and thence further back to the bottom of the silo. At the same time the heating means 2, which has been switched on, strongly heats the conveying element 4 and thereby the powder which is moving upward respectively downward in contact with the inner shell 5 and the outer shell 6, the heat being rapidly and efficiently transferred from the heating means to the powder.

In the embodiment of Fig. 1, the vertical central shaft 1 8 of the screw conveyor 3 is rotatably carried in the silo's bottom wall with the aid of the bearing housing 19 and in the top wall, with the bearing housing 20. The screw conveyor 3 has been connected to the power means constituted by an electric motor 14 over transmission elements such as V-belt pulleys 1 5, 16 and a V-belt 17. The side walls, top wall and bottom wall of the silo 1 are thermally lagged with a view to reducing the heat losses.

In Fig. 2 can be seen the filling aperture 12 for filling powder into the silo, that is, into the interspace of the side walls and the conveyor 4 and for removing moisture from the silo. The bottom of the silo is substantially closed i.e. free from other inlets or outlets than draining aperture 13.

It is possible instead of the screw conveyor used in the embodiment example of the invention to employ any other type of mechanical or even pneumatic mixer or conveyor towards mixing during the drying process.

The embodiment example is meant to illustrate the invention without in any way confining it, and the invention may vary within the scope of the claims following below.

Claims

1. Means for drying and/or storing welding powder or equivalent, comprising a silo with heating means, characterized in that the means comprises a powder mixer, such as a mixer for transporting the powder from the lower part to the upper part of the silo, that the mixer consists of a screw conveyor which has been placed within a tubular conveying element and that the screw conveyor begins and extends from the bottom of the silo substantially to the top of the silo.

2. Means according to claim 1, characterized in that the heating means has been provided in conjunction with the conveying element.

3. Means according to claim 1 or 2, characterized in that the conveying element comprises an inner shell and an outer shell, these defining between themselves a cylindrical interspace, and that in the interspace has been disposed a heating means, such as an electric heating coil.

4. Means according to any one of claims 1-3, characterized in that the silo is shaped at least in part to be downwardly conically tapering, that the mixer with conveying element has been disposed vertically to lift powder from the bottom to the upper part of the silo, and that the bottom of the silo is substantially closed.

5. Means according to any one of claims 1-4, characterized in that the walls of the silo are thermally lagged.

6. Means according to any one of clairns 1=5 characterized in that in the top wall has been provided an aperture for transferring powder into the silo and for removing moisture from the silo.

7. An apparatus for storing and/or drying a powder, which apparatus comprises a vessel for holding the powder, means for heating powder in the vessel and means for mixing and/or conveying the powder in the vessel.

8. A process of storing and/or drying powder, which process comprises heating the powder held within a vessel and mixing and/or conveying the powder in the vessel during heating.

9. An apparatus substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

10. A process substantially as hereinbefore described with reference to the accompanying drawings.