SCREEN PLATE, SCREW PRESS OR THE LIKE FOR TREATMENT OF A SUSPENSION

Abstract: Screen plate, screw press or the like for the treatment of a suspension having through-flow apertures in its surface. Said surface is uneven and said through-flow apertures are provided in said surface irrespective of the location of said surface irregularities. The invention is as well related to a process for producing said screen plate.

Description: Screen plate, screw press or the like for treatment of a suspension This invention relates to a screen plate, screw press or the like provided with a plurality of through-flow apertures, and intended for the treatment of a suspension. The invention is as well in respect of a process for producing said screen plate, screw press or the like. A screen plate of the kind is illustrated by and described in the Swedish patent specification 7201127-2 (publishing number 374 400). It has, however, proved to be very time consuming and laborious to manufacture screen plates constructed in such a manner that the surface is provided with irregularities, such as depressions, elevations, flutes, or the like, which have a uniform direction in relation to the through-flow apertures of the screen plate all over the surface of the plate. When producing a screen plate of this kind, it is common practice first to produce the apertures, whereafter said irregularities are formd in such a manner that the tool for producing the irregularities is being controlled by the position of the apertures, which are arranged in a regular pattern. The object of the present invention is to provide a screen plate, screw press or the like of the kind mentioned above, and a method of producing it, which is more easily produced and, consequently, less cost- consuming in manufacture in spite of the fact that substantially the same favourable result is attained as with the more cost-consuming screen plates, screw presses or the like of the kind known to the art. The aim of the invention has been reached by the screen plate, screw press or the like having a surface provided with irregularities all over the surface without any specific positioning relative to the through-flow apertures of said surface. Extensive comparative tests in practice with the use of a screen plate according to the invention and screen plates manufactured in accord¬ ance with said Swedish patent 7201127-2 show that extremely satisfactory results are obtained with screen plates according to the invention in spite of the simpler and less cost-consuming way of manufacture. The irregularities or unevennesses may be provided for in a plurality of ways, manually or automatically, and may be produced by cutting processes and be given the shape of grooves, depressions, recesses, or the like. OMPI The irregularities in question may, as well, be produced by spraying a material onto the surface of the screen plate, screw press or the like giving an uneven -or granular surface. Such spraying may be provided for either in such a manner that the sprayed material is deposited regularly over said surface, thus providing the surface with a more or less regular pattern of irregularities, or the material may be sprayed in an irregular pattern over said surface. In other methods of providing for said irregularities in the surface of the screen plate, screw press or the like, the surface is exposed to heat making possible a plastic deformation of said surface, or the surface may be exposed to a corrosive chemical causing an irregular etching of the surface of . the screen plate, screw press or the like. After the surface having been provided with irregularities of the kind described above, the through-flow apertures of the screen are produced. Said apertures may be arranged in a regular or irregular pattern over -the surface, the mutual arrangement of the apertures and their positioning relative to any specific irregularities in the screen surface being of no significance for the function of the screen according to the invention. On the other hand, the invention is, of course, not restricted to the method of manufacture in which the apertures are produced after the screen plate having been provided with surface irregularities. However, it is a preferred method to produce the apertures after having produced the surface irregularities. OMPI

Claims: CLAIMS: 1. A screen plate, screw press or the like comprising a surface with through-flow apertures for the treatment of a suspension, characterized by the apertured surface being irregular and uneven and that said through-flow apertures are positioned in said surface distributed thereover without any respect to positioning relative to surface irregularities. 2. A screen plate according to claim 1, said irregularities consisting of furrows on the surface. 3. A screen plate according to claim 1, said irregularities constituting granular elevations or recesses in the surface. 4. A method of producing a screen plate, screw press or the like according to claim 1, comprising through-flow apertures and being intended for the treatment of a suspension, characterized in that the apertured surface is provided with surface-irregularities irrespective of the location of said irregularities relative to said apertures. 5. A method according to claim 4, in which the surface first is provided with said irregularities, whereafter said apertures are machined through the plate. 6. A method according to claim 4 or claim 5, in which said irregularities in the surface are provided for by cutting machining. 7. A method according to claim 4 or claim 5, in which a material providing for an uneven or granular surface of the screen plate is sprayed over said surface. 8. A method according to claim 4 or claim 5, in which the screen surface is exposed to a heat treatment causing a plastic deformation of the surface. -> OMPI

Inventors: MALM KARL GUNNAR, MALM, KARL, GUNNAR
Applicants: KNUTSILPLAOTAR AB, AB KNUTSILPLAOTAR
Application year: 1982
Main classification: D21D5
IPC codes: B01D35, B23P15, B30B9, D21D5, D21F1