GB2074038A

GB2074038A - Strainer

Info

Publication number: GB2074038A
Application number: GB811745A
Authority: GB
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1980-04-22
Filing date: 1981-04-14
Publication date: 1981-10-28
Also published as: FI811150L; IT8167542A0; JPS56165089A; ES8202608A1; DE3015370C2; FR2480814A1; YU104581A; DE3015370A1; SU1058514A3; ES501506A0; BR6100484U

Abstract

An annular strainer for paper stock comprises a stack of identical strainer basket rings 1 spaced apart axially by separate members 2 to define strainer slots between the rings. The rings are of uniform, generally flat cross-section, with a slight taper towards the downstream side, while members 2 are similarly tapered in the opposite direction. Rings and/or members 2 have through holes 6 accommodating clamping screws which connect the two rings at the ends of the stack. The strainer is simple to produce, has a low flow resistance for the fibrous stock to be strained, and there is little tendency for the strainer slots to become blocked. <IMAGE>

Description

SPECIFICATION Strainer basket for use in the paper industry The invention relates to strainer baskets for use in the paper industry.

Such a strainer basket, particularly for use with picking equipment, has become known from German Laid-open Patent Specification No. 27 50 499. In this strainer basket, annular plates are stacked up on top of each other right through, and are held together at the axial ends by stiffening plates. The said arrangement is held together by clamping screws extending inside through-holes provided in the rings. In this design the annular plates have essentially flat boundary surfaces in the planes perpendicular to the axis of the strainer basket and at the points where the strainer holes or strainer slots are provided they have recesses which terminate on one side of each ring in front of the radially outermost edge and on the other side of each ring in front of the radially innermost edge, and overlap each other.The webs left between the recesses are machined away in the overlapping zone, so that the strainer holes or strainer slots are created there. It is obvious that this arrangement is very complicated and does not correspond to the requirements regarding not too great a flow resistance through the strainer basket and the tendency of the latter to become clogged.

The invention is particularly directed to a strainer basket of the kind which is made up at least in part of a stack of mutually-identical strainer basket rings so as to form strainer slots, and is based on the problem of providing a strainer basket which is relatively simple to produce, which can be varied in its construction, which has a relatively low flow resistance for the fibrous stock suspension or the like which is to be strained, and in which there is little tendency for the strainer slots to become blocked.

According to the invention, a strainer basket of the kind referred to above, is characterised in that the strainer basket rings are disc-shaped and have no strainer slots or holes, each strainer basket ring has a substantially constant flat cross-section profile in the axial section of the strainer basket, between all the adjacent strainer basket rings there are intermediate parts spaced out from each other over the circumference of the strainer basket and arranged to form the strainer slots, so that the height of these is in fact given by the height of the intermediate parts, the strainer basket rings have a substantially similar cross-section profile in the axial section of the strainer basket to that of the intermediate parts, and the cross-section profile of the strainer basket rings tapers in the axial section of the strainer basket substantially conically towards the outflow side of the strainer basket, and the corresponding crosssection profile of the intermediate parts consequently tapers to the same extent in the opposite direction.

Further preferred features of the strainer basket according to the invention are set out in the subsidiary Claims.

With this design for the strainer basket a relatively simple structure is achieved, since the individual component parts can also be produced more simply than in the known strainer basket.

The invention will be appreciated in more detail in the following description of the two embodiment examples of strainer baskets in accordance therewith, with reference to the accompanying drawings, in which: Figure 1 is a view of the strainer basket according to one embodiment.

Figure2 is a section on the line II - II of Figure 1 on an enlarged scale.

Figure 3 is a partial axial section on the line Ill - Ill through the strainer basket, again on an enlarged scale.

Figure 4 is a further view similar to Figure 1, of another embodiment of strainer basket, and Figure 5 is a section perpendicular to the axis of the strainer basket shown in Figure 3, with another arrangement of the small plates.

In the Figures, the separate strainer basket rings are designated 1, the intermediate parts arranged between each of the latter are designated 2, the end rings which strengthen the strainer basket structure are designated 3, and the clamping screws which hold the stack of rings together are designated 4 or 10 respectively.

Between each of the rings the strainer holes, i.e.

the strainer slots 5, can be seen, having a substantially horizontal longitudinal extent (perpendicular to the axis of the strainer basket), and, since in the embodiment examples each of the surfaces which bound the strainer basket rings in an axial direction extends at an angle to planes perpendicular to the axis of the strainer basket, and the cross-section of the rings, like that of the intermediate parts 2, is therefore made in the shape of a wedge, it will be seen that the strainer slots 5 are also wedge-shaped, so that they become wider towards the inside, i.e.

towards the inside of the strainer basket, thus, they have an opening angle so that the through-flow takes place here from the outside to the inside of the strainer basket. Naturally, similar conditions apply for through-flow through the strainer basket from the inside of the strainer basket to the outside. In that case, the slope of the cross-section profile of the strainer basket rings and small plates is designed so that the strainer slots become wider from the inside towards the outside.

It would naturally also be possible to make only one of the said boundary surfaces of the strainer basket rings at an angle. The same would then hold good for the corresponding boundary surfaces of the intermediate parts 2. The production of the intermediate parts 2 is carried out expediently from complete rings which are then divided up into the separate intermediate parts. The conicity of the strainer basket rings and consequently of the intermediate parts is chosen at approximately 2 to 5".

The intermediate parts are each made rounded off at the corners, and the axial distance between adjacent boundary surfaces of adjacent intermediate parts, viewed in an axial direction, amounts radially inside to 0.3 mm, while the corresponding axial distance between the strainer basket rings radially outside amounts to approximately 0.2 mm, with a maximum thickness for the strainer basket rings of approximately 1.3 to 2.5 mm.

If conicity is dispensed with in the strainer basket rings and small plates, thus if the opening angle of the strainer slots is dispensed with, which is hardly possible in practice, however, the intermediate parts 2 could similarly be cut directly out of the strip material from which the strainer basket rings are being made. Their wedge-shaped cross-section may, for example, be already pre-formed or it may be produced on the basic strainer basket ring by pressing in a suitable die, or grinding by means of a suitably-shaped grinding disc, which is made as a ring rotating around the strainer basket ring axis with a diameter corresponding to the strainer basket rings and corresponding to the opening angle on the sloping end surface.

In the latter case it is preferable to taper the cross-section profile on only one side, in which case the taper is preferably 3a to 10 .

It will also be seen from Figure 2 that the cross-sections of the strainer basket rings and the intermediate parts in the axial section are approximately equal, but that the radially outer surfaces of the strainer basket rings lie on a larger diameter than the radially outer surfaces of the intermediate parts; the reverse is the case inside the strainer basket. This makes it easier to line up the intermediate parts and the strainer basket rings in the stack; furthermore, due to this overhang, the effective strainer slot height is reduced further below the smallest dimension of the thickness of the intermediate parts 2, so that these can be made thicker than the effective (minimum) strainer slot height by just this difference, which makes their production easier, with their low values of approximately 0.15 to 0.2 mm.

At the same time, the effect of turbulence in the flow, due to its changing from laminarto turbulent flow at the edges and deflection, together with a loosening effect on the fibrous stock held back at the strainer linked with this is also particularly enhanced thereby.

Due to the wedge-shaped cross-section which results in a better straining throughout, and particu marly in a reduced risk of the strainer slots becoming blocked, it is sometimes possible to achieve better mechanical connection and a better reciprocal fixing of the strainer basket rings.

The through-holes 6 are formed by bores in the strainer basket rings and the intermediate parts.

They are also used for the mutual alignment of these, as in the embodiment example shown in Figures 1 to 3, where the clamping screws 4 extend inside the through-holes, and with a relatively coarse fit according to DIN Standards.

These through-holes can also be provided for alignment in the embodiment of Figure 4, possibly with a smaller diameterforthe aligning rods, but they may also be omitted here. The strainer basket rings and intermediate parts are clamped by clamping bolts 10 extending outside them, over the end rings 3.

Figure 5 shows another version wherein the small plates 2 project on the outside beyond the strainer rings 1. In this case, clamping bolts 10 may again extend inside the strainer rings 2, or outside them, and the small plates may be equipped with throughholes 6 for fixing rods.

Claims

1. A strainer basket which is made up at least in part of a stack of mutually-identical strainer basket rings so as to form strainer slots, characterised by the following features: a) the strainer basket rings are disc-shaped and have no strainer slots or holes, b) each strainer basket ring has a substantially constant flat cross-section profile in the axial section of the strainer basket, c) between all the adjacent strainer basket rings there are intermediate parts spaced out from each other over the circumference of the strainer basket and arranged to form the strainer slots, so that the height of these is in fact given by the height of the intermediate parts.

d) the strainer basket rings have a substantially similar cross-section profile in the axial section of the strainer basket to that of the intermediate parts, and e) the cross-section profile of the strainer basket rings tapers in the axial section of the strainer basket substantially conically towards the outflow side of the strainer basket, and the corresponding crosssection profile of the intermediate parts consequently tapers to the same extent in the opposite direction.

2. A strainer basket according to Claim 1, characterised in that the intermediate parts are in the form of small plates.

3. A strainer basket according to any one of Claims 1 to 2, characterised in that the tapering amounts to approximately 20 to 50on one side.

4. A strainer basket according to any one of Claims 1 to 3, characterised in that, with tapering on only one side, this amounts to approximately 30 to 100.

5. A strainer basket according to any one of Claims 1 to 4, characterised in that the radial edges of the intermediate parts project radially relative to those of the strainer basket rings on the outflow side of the strainer basket.

6. A strainer basket according to any one of Claims 1 to 5, characterised in that the cross-section of the intermediate parts in the radial section is approximately rectangular or trapezoidal.

7. A strainer basket according to any one of Claims 1 to 6, characterised in that the strainer basket rings are clamped together by means of screws extending through the small plates.

8. A strainer basket according to any one of Claims 1 to 7, characterised in that the strainer basket rings and small plates are clamped together by clamps extending radially outside them.

9. A strainer basket according to Claim 8, characterised in that the clamps are formed by clamping bolts extending parallel to the axis of the strainer basket, and the end rings which bound the stack of strainer rings, on which the clamping bolts are braced.

10. A strainer basket according to any one of laims 1 to 9, characterised in that it is rotationally symmetrical.

11. A strainer basket constructed, arranged and adapted for use substantially as hereinbefore de scribed with reference to, and as shown in Figures 1 to 3, or 4, or modified as described with reference to and as shown in Figure 5 of the accompanying drawings.