US2926785A - Sieve texture, especially for the bottoms of harp-shaped sieves - Google Patents

Description

Match 1, 1960 H. E. G. SANDER 2,926,785 SIEVE TEXTURE, ESPECIALLY FOR THE BOTTOMS OF HARP-SHAPED SIEVES Filed Jan. 16, 1958 iii".

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wm W .z'm/emon' HANS EDGAR GEORG SANDER mam moving along the bottom of the sieve. tion, it must be taken into consideration United States Patent SIEVE TEXTURE, ESPECIALLY FOR THE BOT- TOMS OF HARP-SHAPED SIEVES Hans Edgar Georg Sander, Brussels,

to Rain, Lehmann & Co. dorf, Germany Application January 16,1958, Serial No. 709,318 Claims priority, application Belgium January 24, 1957 scams. (Cl. 209-401 Belgium, assignor hold or secure the longitudinal wires at the required distance apart but, secondly, they must ensure the transverse connection of the longitudinal wires. These transverse wires are therefore subjected to stressing which is by no means incousiderable as they have to support not only the specific weight of the sieve texture but also to a great extent the load of the material to be screened and In this connecthat, owing to the acceleration of the material being screened caused by the screening machine during the screening operation, considerable forces due to inertia have to be intercepted and the transverse wires are frequently only capable of taking up these forces to an insuificient exent. This is due primarily to the fact that the physical properties of these wires, due to the undulation necessary for spacing the longitudinal wires, are considerably reduced. The notch effect caused by the undulation of the transverse wires proves to be particularly disadvantageous in this respect. Thus it has been found that the tensile strength of an undulated transverse wire is reduced by about 50% as compared with a wire which is straight along its entire length. Such a reduction in tensile strength has a particularly disadvantageous effect in the case of sieve textures in which the gaps or slits between the longitudinal wires are particularly narrow and consequently the transverse wires are relatively thin and must be provided with undulations which are comparatively steep or strongly accentuated. This results in a considerable weakening of the transverse wires which, almost without exception, leads to premature fracture of these transverse wires when the bottom of the sieve is loaded or stressed. The sieve in question therefore becomes useless through the fracture of the transverse wires long before the longitudinal wires are worn out.

It has already been endeavoured to overcome this objection by affording the transverse connections of the texture of the sieve bottoms greater protection against excessive stressing by introducing or vulcanizing rubber strips in the sieve texture, especially so as to keep the frictional coefiicient at the points of-contactbetween the longitudinal and transverse wires as low as possible. The sieve texture constructed in this manner has, however, not been generally introduced in practice because the advantage attained thereby is not proportionate to the extra cost of manufacture necessitated thereby and consequently the texture cannot be described as economical. It has also been proposed to make the transverse wires Aktiengesellschaft, Dussel-' transverse s of the sieve texture of synthetic fibre instead of metal. This measure has, however, also not been particularly successful.

The object of the invention is, therefore, to produce a slotted or slit sieve texture particularly for the bottoms of harp sieves, which, while avoiding the above-mew tioned objections, is at the same time characterized by greater durability and by the special construction of the transverse connecting means. This is attained according to the invention substantially in that, in addition to undulated transverse wires, transverse wires which are fiat or straight along their entire length, that is are not undulated, are also provided as means for connecting the loagitudinal wires in transverse direction. These transverse connecting means in the'sieve texture according to the invention, consist of two kinds of transverse wires, namely the conventional undulated wires which serve chiefly for holding the longitudinal wires of the sieve texture at the desired distance apart, and in addition thereto straight wires or wires which are not undulated, which serve chiefly for imparting greater strength to the sieve texture in transverse direction. As the transverse wires which are flat or straight along their entire length are not previously undulated, they can be made from the material most suitable for the purpose for which the texture is actually to be used. Thus it is possible to select a material which is best suited as regards the desired degree of hardness, elasticity, pliability and flexibility, or generally speaking, which possesses those properties of a mechanical or a chemical nature which appear most desirable for the purpose for which the sieve texture is actually to be used. These straight transverse wires provided according to the invention, may be metallic or nonmetallic. They may also consist of metal wires coated with an elastic substance, such as rubber, synthetic substance or the like. Finally it is also possible to make the straight non-undulated transverse wires so that they actually consist of several separate wires laid side by side.

Several embodiments of the invention are illustrated by way of example in the accompanying drawing, in which:

Fig. 1 shows a sieve texture in plan view;

Fig. 2 is a side view of Fig. 1;

Fig. 3 shows both in detailed plan view and elevation the undulated transverse Wires of the device,

Fig. 4 show both in plan view and elevation the straight transverse wires of the device,

Fig. 5 shows different various cross-sections of straight transverse wires.

The sieve texture for harp-shaped sieve bottoms illustrated in Figs. 1 and 2 consists of spaced juxtaposed longitudinal wires 1 and transverse wires 2 and 3 connecting the longitudinal wires in transverse direction. Whereas the transverse wires 2 determining the spacing of the longitudinal wires are wavy or undulated, as shown in plan view and side elevation in Fig. 3, the transverse wires 3 are straight as shown in the detail view in Fig. 4, that is they are not undulated or wavy. They are of larger cross-section than the undulated transverse wires 2 and impart to the sieve texture great resistance capacity in transverse direction. The non-undulated wires 3 may be made from the material which is actually most suitable for the actual purpose of which the sieve texture is to be used and of different shaped cross-sections.

Fig. 5 shows several different cross-sectional shapes for the straight or non-undulated transverse wires according to the invention. Example a shows a round metal section, whereas Example 15 shows a transverse wire having a core b, of metal with a coating b of elastic material such as rubber, synthetic substance or the like. In the form of construction shown in Example the straight or non-undulated transverse wire consists of two separate wires 0 c placed directly side by side and inthe Example d a transverse wire is shown consisting of a central wire d and two directly adjacent side wires d and d of smaller diameter than the central wire d In Example e the wire is of rhombic cross-section, whereas the wire f is of lenticular shape, g is of semi-circular shape, h is of rectangular cross-section and i has a flattened hexagonal cross-section. I

Without departing from the scope of the invention the transverse wires maybe of any other cross-sectional shape, be composed of separate wires of different construction, differently arranged and in different combinations to those illustrated.

I'claim:

1. Sieve texture for slot sieve bottoms, in particular for harp-shaped sieve bottoms, comprising longitudinal wires parallel to each other and lying in one plane, said longitudinalrwires having spaced crimped portions and enclosing sieve slots in between each other, transverse undulated wires interlacing and connecting said longitudinal wires in transverse direction at said crimped portions and securing them in spaced position, the spaces between said undulated transverse wires being larger than the spaces between said longitudinal wires, and nonundulated transverse wires spaced from one another run ning in a straight line, said undulated as well as said nonundulated wires being interwoven with the longitudinal wires in such a manner that the adjacent non-undulated transverse wires pass alternately over as well as under the same longitudinal wire.

2. Sieve texture as set'forth intclaim 1, wherein the straight non-undulated transverse wires are of larger cross-section than the undulated transverse wires.

'3. Sieve texture as set forth in claim 1, wherein the straight non-undulated transverse wires consist-of metal wires coated with an elastic material.

4; Sieve texture as set forth in claim 1, wherein the straight non-undulated transverse wires, each consist of several separate wires placed directly side by side..

References Cited in the file of this patentv UNITED- STATES PATENTS

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