Flat sieve element

A flat sieve, or a part thereof, has a flat body of elastic material with a rectangular (or square) frame spanned by a plate of lesser depth with a multiplicity of throughgoing parallel slots and intervening rows of shorter slots interrupted by solid transverse webs which are integral with crossbars intersecting only the lower portions of the longer, throughgoing slots. The length of the shorter slots may be about one-tenth that of the longer slots.

CROSS-REFERENCE TO RELATED APPLICATION 
This application contains subject matter disclosed in our copending 
application Ser. No. 317,381 filed Nov. 2, 1981 now abandoned. 
FIELD OF THE INVENTION 
Our present invention relates to a sieve, or to a part of such sieve, which 
has a four-sided (preferably rectangular or square) frame whose opening is 
spanned by a slotted horizontal plate for the sifting of solid particles 
or the drainage of liquids from a mass placed thereon. 
BACKGROUND OF THE INVENTION 
A sieve of this type is known, for example, from German printed application 
No. 2,634,934. In an effort to combine a filtering or drainage area of 
large relative cross-section with structural stability of the carrier 
plate, that known sieve has a number of parallel throughgoing 
slots--extending over substantially the full length of width of the 
plate--alternating with rows of shorter slots interrupted by solid 
portions of the plate surface. Our copending application Ser. No. 317,381 
now abandoned, whose disclosure is incorporated by reference into the 
present one, describes and shows a similar sieve element with either 
partly or fully throughgoing slots separated by ribs whose lower portions 
are interconnected by crossbars of different height. 
Care must be taken in such sieves that solid particles of the mass being 
filtered or dewatered do not penetrate into the slots and deform the ribs 
bounding same, especially when the plate spanning the frame is made of 
elastic or otherwise yieldable material such as polyurethane, for example. 
Aside from a possible clogging of the slots by particles wedged therein, 
the resulting local widening thereof impairs the utility of the sieve as a 
means for the classification of comminuted solids, i.e. for separating 
particles with sizes above and below a certain threshold from one another. 
OBJECT OF THE INVENTION 
The object of our present invention, therefore, is to provide an improved 
sieve element of the general type referred to which combines great 
structural stability with a relatively large open area for the draining or 
the filtering of a particulate mass. 
SUMMARY OF THE INVENTION 
A sieve element according to our invention has a basic structure similar to 
that disclosed in our copending application Ser. No. 317,381 now 
abandoned, namely a four-sided horizontal frame integral with a slitted 
plate spanning its interior in order to support a mass to be drained, 
filtered or classified, this plate being formed with a multiplicity of 
ribs defining a plurality of continuous throughgoing slots and intervening 
rows of shorter slots parallel to a pair of frame sides. In accordance 
with our present improvement, crossbars perpendicular to the slots 
underlie transverse webs separating the shorter slots of a row from one 
another. 
Preferably, the ribs have undersides coplanar with those of the crossbars 
and rise above the latter to the level of the upper surfaces of the 
transverse webs, thus forming a sturdy grid. Such a carrier plate and its 
frame can be readily molded in one piece from plastic material which may 
have a certain elasticity to facilitate the fitting of the sieve element 
into a larger mounting frame.

SPECIFIC DESCRIPTION 
As shown in the drawing, a sieve element 1 according to our invention 
comprises a rectangular frame 2 whose opening is spanned by a horizontal 
carrier plate forming a multiplicity of parallel ribs 8 which together 
with two frame sides define continuous throughgoing slots 3 and rows 4 of 
shorter slots 5. The shorter slots 5 of any row are separated by 
transverse webs 7 which terminate at the longer slots 3 and directly 
overlie respective crossbars 6 intersecting the throughgoing slots 3 only 
in the lower half of their cross-section. As will be apparent from FIG. 2, 
the carrier plate consisting of members 6, 7 and 8 lies only in the upper 
half of frame 2 and is molded integral therewith from plastic material; a 
middle rib', however, extends over the full height of the frame. Molding 
is facilitated by a downward tapering of all the ribs, and of the strips 
defining the frame 2, in the region below the upper level of crossbars 6; 
these crossbars may be similarly tapered. FIG. 2 further shows that the 
sieve element 1 is fitted into a larger mounting frame 9 which could have 
a number of rectangular cutouts receiving several such sieve elements. 
With the upper surfaces of frames 2 and 9 as well as those of ribs 8 and 
webs 7 all lying in a common horizontal plane, the goods to be treated can 
be readily spread over all the sieve elements. 
We prefer to make the length of each of the shorter slots 5 equal to about 
one-tenth the length of the slots 3, even though that length ratio may 
range more generally between approximately 1:5 and 1:20. Thus, for 
example, slots 3 may have a length of 120 mm while each slot 5 is 12 mm 
long. Both sets of slots should have the same width, e.g. 0.5 mm in a 
specific instance. The width of the webs 7 and the crossbars 6 should be a 
small fraction of the length of slots 5, e.g. about a third thereof as 
shown.