CA2319957A1

CA2319957A1 - Strainer for a screw press dewatering apparatus

Info

Publication number: CA2319957A1
Application number: CA 2319957
Authority: CA
Inventors: Frank Grund
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-09-18
Filing date: 2000-09-18
Publication date: 2002-03-18

Abstract

A strainer for a screw press dewatering apparatus includes a body having an exterior surface, a flow passage extending through the body, and a plurality of drainage apertures extending from the flow passage to the exterior surface. The cross section of the flow passage is a polygon.
The polygonal cross-section provides a number of sides and angles. While compressed material will tend to rotate within a flow passage of a circular cross-section, the sides and angles of a polygonal cross-section resist rotation and facilitate the material being driven forward by the flightings upon rotation of the screw press.

Description

TITLE OF THE INVENTION:
Strainer For A Screw Press Dewatering Apparatus FIELD OF THE INVENTION
The present invention relates to strainer for a screw press dewatering apparatus and, in particular, such an apparatus used in the dewatering of wood pulp.
BACKGROUND OF THE INVENTION
Apparatus used in dewatering wood pulp, have a conical or cylindrical strainer. A rotational screw is used to press wood pulp into the strainer. As the material is pressed, liquid from the wood pulp is forced out through a series of holes in the body of the strainer.
Such an apparatus for dewatering wood pulp is subject to blockages in which compressed wood pulp rotates with the screw, but does not advance. Every time one of these blockages occurs servicing is required, and production is lost. If the blockage is not promptly detected a fire can result, as the wood pulp become highly compressed and devoid of moisture.
SUN~iARY OF THE INVENTION
What is required is an improved strainer design which facilitates the advancement of material.
According to the present invention there is provided a strainer for a screw press dewatering apparatus which includes a body having an exterior surface, a flow passage extending through the body, and a plurality of drainage apertures extending from the flow passage to the exterior surface. The cross section of the flow passage is a polygon.
With the strainer, as described above, the polygonal cross-section provides a number of sides and angles. While compressed material will tend to rotate within a flow passage of a circular cross-section, the sides and angles of a polygonal cross-section resist rotation and facilitate the material being driven forward by the flightings upon rotation of the screw press. The polygonal strainer has a much higher compression ratio, as compared to a round strainer, which enables higher efficiency in dewatering to be achieved.
Although beneficial results may be obtained through the use of the strainer, as described above, the best results have been obtained when the polygon is an octagon. The eight sides of an octagon resist rotation and yet maintain sufficient contact with the flightings of the screw press to keep the drainage apertures clear.
Although beneficial results may be obtained through the use of the strainer, as described above, it is preferred that an octagonal screen liner be placed within the flow passage.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, wherein:
FIGURE 1 is a bottom plan view of a strainer for a screw press dewatering apparatus constructed in accordance with the teachings of the present invention.
FIGURE 2 is a side elevation view, in section, of the strainer illustrated in FIGURE 1.
FIGURE 3 is a detailed side elevation view of one of the sides of the strainer illustrated in FIGURE 1.
FIGURE 4 is a side elevation view, in section, of the strainer illustrated in FIGURE l, showing the position of flightings from the screw press.
FIGURE 5 is a bottom plan view, in section, of the strainer illustrated in FIGURE 1, with screen liner.
DETAILED DESCRIPTION O

F THE PREFERRED EMBODIMENT
The preferred embodiment, a strainer for a screw press dewatering apparatus generally identified by reference numeral 10, will now be described with reference to FIGURES 1 through 5.
Structure and Relationship of Parts:
Referring to FIGURE 1 and 2, strainer 10 is a cone which has a body 12 with an exterior surface 14 and a flow passage 16 extending through body 12. Flow passage 16 has an first end 18 and a second end 20 and is bounded by eight sides 22 which extend longitudinally from first end 18 to second end 20.
Referring to FIGURE 1, a cross section of flow passage 16 is an octagon. Referring to FIGURE 3, each of eight sides 22 of flow passage 16 have a plurality of drainage apertures 24 which extend from flow passage 16 to exterior surface 14.
Operation:
The use and operation of strainer 10 which incorporated into a screwpress dewatering apparatus will now be described with reference to FIGURES 1 through 5. Referring to FIGURE 1, when strainer 10 for a screwpress dewatering apparatus is in use, material requiring dewatering enters strainer 10 at first end 18 of flow passage 16. Referring to FIGURE 4, a rotational screw 26 is employed to press liquid from material by pressing material along flightings 28 through flow passage 16 toward second end 20. As rotational screw 26 rotates, material is carried from first end 18 of flow passage 16 toward second end 20. In the past problems have been encountered with similar devices due to material becoming compacted and rotating with screw 26. When strainer 10 is used, material does not rotate with rotational screw 26 as sides 22 of flow passage 16 create angles which resist rotation and facilitate material being driven forward by flightings 28. Sides 22 of flow passage 16 maintain sufficient contact with flightings 28 of rotational screw 26 to keep drainage apertures 24 clear. As rotational screw 26 is rotated, material is compressed so that liquid is forced from material and exits strainer 10 through drainage apertures 24 in sides 22 of flow passage 16.
Variations and Alternative Embodiments:
Although cross-section for the flow passage of strainer is an octagon, there are other polygonal cross-sections that can be used to address a blockage problem. A pentagon or a hexagon would work, but would not be able to keep the drainage 10 apertures as clear.
Referring to FIGURE 5, in some applications, it may be desirable to provide a screen liner 30 lining flow passage 16.
Screen liner 30 assists in preventing drainage apertures 24 from becoming clogged. The cross-section of screen liner 30 will, of course, be the same of the cross-section of flow passage 16; which in this case is an octagon.
The octagonal cone has a much higher compression ratio, as compared to a round cone, which enables higher efficiency in dewatering to be achieved.
It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the Claims.

Claims

1. A strainer for a screw press dewatering apparatus, comprising:
a body having an exterior surface, a flow passage extending through the body, and a plurality of drainage apertures extending from the flow passage to the exterior surface, the cross section of the flow passage being a polygon.

2. The strainer as defined in Claim 1, wherein the polygon is an octagon.

3. The strainer as defined in Claim 1, wherein the flow passage has a screen liner.

4. A strainer for a screw press dewatering apparatus, comprising:
a body having an exterior surface, a flow passage extending through the body, and a plurality of drainage apertures extending from the flow passage to the exterior surface, the cross-section of the flow passage being an octagon; and a screen liner lining the flow passage the cross-section of the screen liner being an octagon.