GB2174633A

GB2174633A - Welding

Info

Publication number: GB2174633A
Application number: GB08607080A
Authority: GB
Inventors: Kenneth James Gutteridge
Original assignee: N Greening Ltd
Current assignee: N Greening Ltd
Priority date: 1985-03-21
Filing date: 1986-03-21
Publication date: 1986-11-12
Also published as: GB8507424D0; GB8607080D0; GB2174633B

Abstract

A sieve element 10, shown inverted, comprises a plurality of wedge wires 12 arranged parallel but spaced by a gap chosen according to the material to be allowed to pass through the element. The wires 12 are secured by cross members 14 fusion welded thereto at 16 by a tungsten inert gas welding technique. <IMAGE>

Description

SPECIFICATION Welding This invention concerns welding particularly for the manufacture of metal sieve elements.

Metal sieve elements for screening apparatus particularly for sizing and/or deliquifying particulate materials, such as aggregates, are often made from wire, especially wedge wire.

Each element comprises a plurality of wires side by side but spaced by a desired distance according to the size or nature of the materials to be allowed to pass through the element and cross members to which the wires are secured. The wires may be looped with the cross members through aligned loops of each wire but the present invention is concerned with elements in which the wires have cross members welded thereto.

At present a resistance welding technique is used for the manufacture of these metal sieve elements but that technique has a number of disadvantages. Firstly, in the resistance welding technique welding has to be carried out on both sides of the cross members using filler wire each time to give adequate strength to the weld and thus to the element. This repetition of the welding operation is, of course, time consuming and hence costly.

Secondly, for some purposes sieve elements are required which have deep cross members.

Because of their depth and consequently higher electrical resistance than thinner cross members, however, these cross members hinder the formation of proper welds so that such elements can be weak in some areas.

Thirdly, in the resistance welding technique, a large electrode is used that generates considerable heat. This heat expands the wedge wires and cross members causing distortion thereof. As the welding operation is repeated for each cross member the gaps between adjacent wedge wires can be altered considerably from their original setting. Thus, wedge wire sieve elements produced by this technique are not necessarily as accurate as is desirable.

An object of this invention is to provide a method of producing metal sieve elements that does not suffer from the above mentioned disdvantages.

According to this invention it is proposed that a fusion type welding technique be used for producing metal sieve elements particularly wedge wire screen elements.

Preferably a tungsten inert gas (TIG) welding technique is used to produce sieve elements.

In this technique, a workpiece is shrouded in an inert gas atmosphere and a tungsten electrode is used to pass an arcing electric current to the workpiece. No filler wire is required to form a weld as this is provided by melting that part of the workpiece to which the electric current is passed.

In the case of wedge wire sieve elements arcing is preferably to the cross members and directly to that part of the cross members closest to the wedge wires. This causes melting of the cross member metal into the gaps between the wedge wires to form the weld.

A single welding operation on each cross member is usually all that is required to form a sufficiently strong weld for the sieve element to be able to stand upto the rigorous conditions in which it is to be used.

As the amount of heat generated in the TIG technique is lower than in the resistance welding technique and as only one welding operation per cross member is needed, expansion of the cross members/wedge wires and hence inconsistent gaps between the wires is no longer such a serious problem.

Furthermore, the TIG technique is suitable for deep cross members as their size and electrical resistance is not a factor in the effectiveness of the TIG technique.

In summary a fusion welding technique, such as TIG, can be both efficient and economical for the production of sieve elements, such as wedge wire sieve elements or any other wire type sieve element. Furthermore the accuracy of such elements can be greater than corresponding elements made by other techniques.

The present invention also comprehends sieve elements such as wedge wire sieve elemens produced by a fusion welding technique, such as TIG.

The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a section of a wedge wire sieve element produced by the TIG welding technique; and Figure 2 shows a reduced side view of the element of Fig. 1.

Referring to the drawings, a sieve element 10, shown inverted, comprises a plurality of wedge wires 12 arranged parallel but spaced by a gap chosen according to the material to be allowed to pass through the element. The wires 12 are secured by cross members 14 welded thereto at 16. The cross members 14 shown here are of the deeper section type but the invention is equally applicable to elements that have lesser section cross members.

As can be seen more clearly in Fig. 2 the welds 16 are formed on one side only of the cross members 14 and the weld material is actually melted from the cross members themselves. This is achieved by the tungsten inert gas welding technique in which the workpiece is shrouded in inert gas and the arcing current is directed at the desired weld position by a tungsten electrode.

1. A method of producing metal sieve elements including using a fusion type welding

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Welding This invention concerns welding particularly for the manufacture of metal sieve elements. Metal sieve elements for screening apparatus particularly for sizing and/or deliquifying particulate materials, such as aggregates, are often made from wire, especially wedge wire. Each element comprises a plurality of wires side by side but spaced by a desired distance according to the size or nature of the materials to be allowed to pass through the element and cross members to which the wires are secured. The wires may be looped with the cross members through aligned loops of each wire but the present invention is concerned with elements in which the wires have cross members welded thereto. At present a resistance welding technique is used for the manufacture of these metal sieve elements but that technique has a number of disadvantages. Firstly, in the resistance welding technique welding has to be carried out on both sides of the cross members using filler wire each time to give adequate strength to the weld and thus to the element. This repetition of the welding operation is, of course, time consuming and hence costly. Secondly, for some purposes sieve elements are required which have deep cross members. Because of their depth and consequently higher electrical resistance than thinner cross members, however, these cross members hinder the formation of proper welds so that such elements can be weak in some areas. Thirdly, in the resistance welding technique, a large electrode is used that generates considerable heat. This heat expands the wedge wires and cross members causing distortion thereof. As the welding operation is repeated for each cross member the gaps between adjacent wedge wires can be altered considerably from their original setting. Thus, wedge wire sieve elements produced by this technique are not necessarily as accurate as is desirable. An object of this invention is to provide a method of producing metal sieve elements that does not suffer from the above mentioned disdvantages. According to this invention it is proposed that a fusion type welding technique be used for producing metal sieve elements particularly wedge wire screen elements. Preferably a tungsten inert gas (TIG) welding technique is used to produce sieve elements. In this technique, a workpiece is shrouded in an inert gas atmosphere and a tungsten electrode is used to pass an arcing electric current to the workpiece. No filler wire is required to form a weld as this is provided by melting that part of the workpiece to which the electric current is passed. In the case of wedge wire sieve elements arcing is preferably to the cross members and directly to that part of the cross members closest to the wedge wires. This causes melting of the cross member metal into the gaps between the wedge wires to form the weld. A single welding operation on each cross member is usually all that is required to form a sufficiently strong weld for the sieve element to be able to stand upto the rigorous conditions in which it is to be used. As the amount of heat generated in the TIG technique is lower than in the resistance welding technique and as only one welding operation per cross member is needed, expansion of the cross members/wedge wires and hence inconsistent gaps between the wires is no longer such a serious problem. Furthermore, the TIG technique is suitable for deep cross members as their size and electrical resistance is not a factor in the effectiveness of the TIG technique. In summary a fusion welding technique, such as TIG, can be both efficient and economical for the production of sieve elements, such as wedge wire sieve elements or any other wire type sieve element. Furthermore the accuracy of such elements can be greater than corresponding elements made by other techniques. The present invention also comprehends sieve elements such as wedge wire sieve elemens produced by a fusion welding technique, such as TIG. The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a section of a wedge wire sieve element produced by the TIG welding technique; and Figure 2 shows a reduced side view of the element of Fig. 1. Referring to the drawings, a sieve element 10, shown inverted, comprises a plurality of wedge wires 12 arranged parallel but spaced by a gap chosen according to the material to be allowed to pass through the element. The wires 12 are secured by cross members 14 welded thereto at 16. The cross members 14 shown here are of the deeper section type but the invention is equally applicable to elements that have lesser section cross members. As can be seen more clearly in Fig. 2 the welds 16 are formed on one side only of the cross members 14 and the weld material is actually melted from the cross members themselves. This is achieved by the tungsten inert gas welding technique in which the workpiece is shrouded in inert gas and the arcing current is directed at the desired weld position by a tungsten electrode. CLAIMS

1. A method of producing metal sieve elements including using a fusion type welding technique.

2. A method as claimed in claim 1 in which the welding technique is a tungsten inert gas (TIG) welding technique, in which a workpiece is shrouded in an inert gas atmospher and a tungsten electrode is used to pass an arcing electric current to the workpiece.

3. A method as claimed in claim 1 or 2 wherein for wedge wire sieve elements arcing is to cross members and directly to that part of the cross members closest to the wedge wires, whereby cross member metal is melted in to gaps between the wedge wires to form the weld.

4. A sieve element produced by a method as claimed in claim 1, 2 or 3.

5. A wedge wire sieve element produced by a method as claimed in claim 1, 2 or 3.

6. A method of producing metal sieve elements substantially as hereinbefore described with reference to the accompanying drawings.

7. A metal sieve element substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.