More particularly, the invention occupies itself with a cylindrical socalled bar-type strainer for use in screw presses of the kind defined above.

The cylindrical strainer member in such screw presses is often subjected to wearing and tearing giving rise to leakages between the strainer wall and the worm screw. This reduces the capacity of the screw press.

It is previously known to use a perforated plate bent into cylindrical shape as a strainer element; confer Norwegian patent specification No. 168,401. Such per- forated plate-strainers are especially liable to crack upon extensive wearing and tearing or unusual loads.

British patents Nos. 1,163,913 and 1,282,448 as well as U.S. patent No. 4,848,223 treat of screw presses for various purposes such as drying elastomeric materials, extracting liquids from tannery waste or draining fibrous materials, respectively.

As per se, it is known to build up a cylindrical strainer element by means of longitudinal flat steel bars, mutually spaced circumferentially and engaging into intertooth spaces between teeth of internally toothed, lateral support rings, and wherein, in connec- tion with each support ring, stretching bands are dis- posed in order to, upon a possible after-tightening, to move the longitudinal bars radially inwardly into posi- tions at a short distance from those portions of the screw conveyor being the outermost at any time.

Dependent on consistence, structure and liquid content of the material being treated in the screw press, it might be desirable or necessary to change the slot opening between the bars. Using the flat steel bars as such for strainer slot adjusting purposes, much mate- rial would be required for the broadest bars, simul- taneously as one could not always have maintained the same inner and outer diameter of the strainer cylinder.

When changing the inner diameter proportions, the worm screw must be replaced by a screw of another dimension, and such a measure could cause a time-consuming ten- sioning of the bars.

The object of the invention has been, using simple and inexpensive means, to remedy these disadvantages and deficiencies of prior art technique and, thus, provide a bar-type strainer for a screw press wherein the slot openings (the strainer slots) can be adjusted simply and rapidly, without such adjustment giving rise to re- quirements for changes in adjacent components or other parts.

According to the invention, said object is achieved by shaping and designing the bar-type strainer in accor- dance with the characterizing clause of claim 1.

According to the invention, between opposing faces of adjacent longitudinal strainer bars, dividing plates are mounted, said dividing plates having locally posi- tioned distancers which, at each dividing plate, rest against said opposing strainer bar faces. Upon adjust- ment of said intermediate spaces by means of the divid- ing plates, one may use the same strainer bars as be- fore and, thus, also the same support rings with unchanged internal toothing, as only the dividing plates have to be replaced by a larger or smaller thickness dimension, dependent on the desired slot opening. The locally placed distancers of the dividing plates, e.g. in the form of bulb-like projections dis- tributed longitudinally in e.g. two rows, one at each longitudinal edge, provide an easily releasable, yet reliable attaching device. If one, in accordance with prior art technique, would try to reduce the inter- mediate strainer slots by means of the strainer bars approximately as much as is possible by means of the intermediate dividing plates, the teeth in the internal toothing of the support rings would have become so nar- row circumferentially that their structural strength

could not have withstood the bending strains normally prevailing.

An examplary preferred embodiment is explained in the following, reference being made to the accompanying drawings, wherein: Figure 1 shows a perspective view, seen obliquely from above, of a screw press where some components have been omitted, but where a portion of the bar-type strainer is shown, surrounded by one support ring and one ten- sioning band; Figure 2 is a perspective view, seen obliquely from above, of a bar-type strainer during construction, showsing end pieces, longitudinal suspension, lateral support rings and tensioning bands, but where only a pair of strainer bars have been mounted; Figure 3 shows an end view of figure 2, the closest situated support ring's toothing appearing as well as two upper strainer bars engaging two adjacent inter- tooth spaces; Figure 4 shows a partial view on a larger scale, corre- sponding to the encircled detail IV in figure 3, illus- trating the two adjacent, longitudinal strainer bars with an intermediate dividing plate; Figure 5 shows an end view/cross section corresponding to figure 3, the bar-type strainer appearing in a fin- ished built up condition, having lateral support rings and longitudinal strainer bars and intermediate divid-

ing plates, in the area of a support ring and its sus- pension; Figure 6 is a similar cross section in the area of a tensioning band; Figure 7 is a half longitudinal partial section of a worm screw and the assignment of a dividing plate; Figure 8 shows the same, a strainer bar being assigned thereto; Figure 9 is a detail view in cross section correspond- ing to figure 4, showing an internally toothed support ring portion, where three strainer bars and two inter- mediate, relatively thin dividing plates have been dis- posed; Figure 10 shows a partial cross-sectional view corre- sponding to figure 9, and where the dividing plates are shown to be relatively thick.

In figures 1 and 2, reference numeral 10 denotes a cut cylindrical cover serving to receive and collect liquid pressed out from a mass by means of a worm screw 12 of a screw press, figures 7 and 8, cooperating with a con- centrical strainer cylinder in the form of a bar-type strainer 14, the dewatered, drier mass phase being re- ceived at the downstream end of the worm screw, the cover 10 having an outlet for the liquid phase sepa- rated therefrom. It may, of course, be used containers of other types to take care of liquid successively pressed out.

In figure 1 the drive motor 16 of the screw press ap- pears, which through an appropriate transmission de- vice, e.g. a toothed wheel gearing, rotates the worm screw 12 within the bar-type strainer 14. The bar-type strainer 14 is assembled of longitudinal strainer bars 18 distributed and mutually spaced circumferentially and having therebetween intermediate, longitudinal di- viding plates 20, see i.a. figure 4, and surrounded by support rings 22 and tensioning bands 24 distributed and spaced longitudinally, the bands 24 being stretched and tensioned in a manner known per se. Suspension ele- ments 34 distributed and spaced circumferentially ap- pears from figures 1 - 3 and 5.

Pipe bend-shaped connecting pieces or studs for supply hoses transporting material to be separated are denoted by 28 and 28'. They pass into a downwardly tapering in- let chamber 30 in the area of the upstream end (not shown) of the worm screw 12. These known and in part conventional arrangements in screw presses of the kind concerned are assumed to belong to the knowledges of an average person skilled in the art and are, conse- quently, not further described.

End pieces 32, 32', see particularly figure 2, serve as fasteners for longitudinal suspension members 34. The lateral support rings 22 which are parallel to the end pieces 32, 32', have internal toothing, the teeth being denoted at 38 and the intertooth spaces at 40. The in- tertooth spaces 40 of the support rings 22 are each in- tended to accommodate a longitudinal strainer bar 18 placed radially inside thereof, said bar, usually, con- sisting of flat steel. The width of the tooth 38, i.e.

extent circumferentially, determines the spacing be- tween the strainer bars 18, corresponding to the strainer aperture/slot.

In order to adjust the width of this strainer slot without having to replace the support rings and without having to modify other components, parts or adjacent portions of the screw press, said dividing plates 20 have been mounted in between adjacent strainer bars 18 in accordance with the invention. The dividing plates 20 may be provided with cavities complementarily shaped to fit the support ring cross section, figure 7, and, as shown in figure 4 and figure 10, are relatively thick, while they are shown to be relatively thin in figure 9. The strainer slot SS is indicated in figure lo.

Each dividing plate 20 is, at each side thereof, pro- vided with two longitudinal rows of locally placed, e.g. bulb-like projections 42 forming distancers in re- spect of adjacent strainer bars 18. The outer points of the distancers 42 rest against opposing faces of the strainer bars 18 og maintain the dividing plate 20 in an exact intermediate position between adjacent strainer bars 18, in order to maintain equal width of the strainer slots around the circumference of the bar- type strainer 14.