IE42554B1 - Rotary separator screen particularly suited for the primary screening of city solid wastes - Google Patents

Abstract

This invention relates to an improved screen for use in a rotating screen separator suitable for primary screening of city solid wastes to remove objects in the waste such as sheeting, strapping and cordage. The dimensions of the openings in the surface of the screen are greater in a direction parallel to the direction of rotation of the screen than in a perpendicular direction. The prior art separators become easily clogged by such objects and the novel screen of the present invention has effectively overcome these problems.

Description

The invention relates to a rotary screen particularly suitable for the primary separation of city solid wastes or refuse.

It is known that in the processing of city solid wastes there is needed a first screening of the said wastes in such a way as to separate particularly encumbering and useless materials within such wastes, such as with respect to their size and their nature.

The already known separators are generally not useful as any kind of a shaking or vibrating separator and also rotating separators having a perforated surface, or shell is likely to become clogged with the particular waste material to be treated and that is placed on it, or within it. Therefore time is required for cleaning the separator and restoring its working capacity.

Furthermore, from studies and experience, it has been stated that, in any case, for the first screening of city solid wastes shaking or vibrating separators are to be rejected because of the extremely heterogeneous nature of the material to be treated. On the other hand, the known rotary screens do not lend themselves well to the first screening of city solid wastes as, in connection with the heterogeneity of the material to be treated and more in particular in connection with the presence of sheeting and strips of different nature and sizes, the holes of the screen will be very easily clogged. In other words, it was possible to - 2 42554 ascertain that in a rotating screen the waste sheetings, as also the waste strips, are inclined to bridge the holes and therefore to obstruct very quickly the holes of the screen.

Therefore, in connection witfi the aforemade observations - that were made during some tests - it was stated that a screen suitable for the primary separation of city solid wastes must be a rotary one, but with holes having a length several times greater than their width.

It is therefore an object of the present invention to provide a rotary screen, that is in particular suited for the primary separation of city solid wastes, but that can also be used for the separation of heterogeneous material in general, and in which the already mentioned disadvantages of the previous rotating and vibrating screens are obviated.

In accordance with the invention there is provided a rotary screen for the separation of heterogeneous material, comprising a rotary cylinder provided with a plurality of openings in its cylindrical wall, which cylinder, in use of the screen, receives the material to be separated at one end, the dimension of any one of said openings as measured in the direction along a circumference of the cylinder at any position in the opening being several times greater than the dimension of the openings as measured in the direction along a generatrix of the cylinder at any position in the opening, and said cylinder comprising a plurality of annular members formed of flat strip material disposed coaxially in spaced-apart parallel planes, and a plurality of longitudinal members formed of flat strip material disposed parallel to the cylinder axis and interconnecting the annular members, the said openings each being delimited by two annular members and two longitudinal members.

An embodiment of the invention is hereinafter described, by way of a nonlimitative example, with reference to the accompanying drawings in which:Figure 1 is a schematic perspective view of a separating screen; and Figure 2 is an end elevational view of a modification of the screen.

With reference to the said drawings arid more in particular to Figure 1, the rotary screen comprises a series ol side-members 11, disposed along l.lie - 3 4 2 554 generatrices of a cylinder shaped body, that forms the screen. To the said side-members 11 are fixed, in any convenient way, spaced-apart rings, or meridian elements 12. As shown, the side-members 11 and rings 12 are formed of flat strip material. Such elements 12, in co-operation with the side members 11, produce, in this way, on the perimeter of the cylinder shaped body a series of openings 13 having a length several times greater than their width. It will be understood that in use of the screen waste material to be separated is fed into one end of the cylinder. : The openings 13 succeed one after the other along the perimeter of the cylinder-shaped body and have a length, that is limited by the side members 11. Therefore, on the cylinder and in each section of the same are as many openings 13 as there are side members.

The number of the side members and their positioning are, of course, a function of the load that the screen must bear during the screening operations.

In the embodiment of Figure 1, four side members 11 are shown. Such a number is not a limitative one, but is only one example.

We have found that the screened material easily passes through the openings 13, whereas the oversize passes out of the device from the free end of the screen i.e. the oversize of those materials, that, if fed to a following cycle of working, will cause problems and will damage the subsequent machinery.

' Furthermore we have found that sheetings, or strips, or also cordage, etc. even if they are inclined to overlap the side members 11 do not succeed in clogging the openings 13 and therefore the openings always remain open and as a consequence a frequent maintenance of the screen is not required, as would be the case with other screens.

Figure 2 shows a modification for eliminating the possibility that the sheetings such as ones of plastics and.paper, might wrap themselves on the side members 11, and more precisely on the lengths of the side members 11 that delimit the openings 13. To this end, as shown in Figure 2, in connection with the side members there are provided transport blades 14 covering the side members and that - 4 42554 provide for the removal of this sheet material. In a preferred embodiment the blades 14 have such a cross-section that the combined perimeter of the said blades and the surface of the side members remaining exposed has a length greater than the greatest dimension of a plastics or paper sheet, that is likely to be found within the screen. Therefore such a sheet can never cover the blade and the side member and embrace them wholly wrapping itself on these elements.

Of course, the number of the side members 11 or the number of the meridians 12 will be selected in connection with the particular material to be screened and the spacing of the meridians will be changed in connection with the nature of this material.

Claims (5)

1. A rotary screen for the separation of heterogeneous material, comprising a rotary cylinder provided with a plurality of openings in its cylindrical wall, which cylinder, in use of the screen, receives the material to be separated at one end, the dimension of any one of said openings as measured in the direction along a circumference of the cylinder at any position in the opening being several times greater than the dimension of the opening as measured in the direction along a generatrix of the cylinder at any position in the opening, and said cylinder comprising a plurality of annular members formed of flat strip material disposed coaxially in spaced-apart parallel planes, and a plurality of longitudinal members formed of flat strip material disposed parallel to the cylinder axis and interconnecting the annular members, the said openings each being delimited by two annular members and two longitudinal members.

2. A screen, according to Claim 1, comprising four equi-spaced longitudinal members.

3. A screen, according to any one of Claim 1 or Claim 2, in which each longitudinal member has a blade portion extending radially in a direction towards the cylinder axis.

4. A rotary screen substantially as hereinbefore described with reference to,

5. - 5 42554 and as illustrated in, Figure 1 or Figure 1 as modified by Figure 2, of the accompanying drawings.