Screen device with slot-shaped openings

A screen device including a multitude of parallel rods between which are located the sorting slots. The rods are held in position by supporting elements, which are connected with carriers. The respective cover elements are located at the faces of the rods. Due to their special design, the cover elements may be detachable. The screen devices may be used, for example, in the paper-making industry as cylindrical screen baskets or plane screens.

CROSS-REFERENCE TO RELATED APPLICATION 
The present application claims priority under 35 U.S.C. .sctn. 119 of 
German Patent Application No. 196 51 643.9 filed Dec. 12, 1996, the 
disclosure of which is expressly incorporated by reference herein in its 
entirety. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a screen device for sorting fiber 
suspensions with a multitude of substantially parallel aligned rods. 
Between the parallel rods are sorting slots or sorting slits which are 
fixed in the supporting elements and cover elements. 
2. Discussion of Background Information 
It is known to use this type of device for sorting fiber suspensions. The 
fibers contained in the suspension are to pass through the screen, while 
undesired solid components are rejected at the slot (or slit) and removed 
from the screen device. Another conceivable use for the device is the 
separation of varying fiber components. Due to the fact that the openings 
are substantially longitudinal in shape, i.e., slots or slits, the fibrous 
particles pass through these slots more easily than cubic particles, even 
if both particles have a similar order of magnitude. This type of sorting 
technology, therefore, has an excellent capability of removing non-fibrous 
interfering substances from the fiber suspension. This, however, requires 
dimensional stability and a high precision of the slot shape on the entire 
screen surface. 
In many cases, such screen devices are subject to severe wear and thus need 
replacing. 
A method for producing rod wire or screen or sieve baskets is shown in DE 
39 27 748 A1, wherein the sectional rods are clamped by an elastic 
deformation of the supporting rings that include recesses for holding the 
rods. Sectional rods, which are particularly suitable for this type of 
production method, are used. This method allowed one to considerably 
reduce the production costs, however, when using this type of screen 
basket, certain restrictions could not be ruled out, especially when 
subjected to intensive mechanical loads. 
Screens or screen elements with good stability and excellent surface 
quality may also be produced according to a method described in DE 42 14 
061 A1. There, the rod-shaped profiles are fixed by using a 
high-temperature soldering method. The result is excellent, but the 
process is burdensome and expensive. 
EP 0 724 037 A2 describes slot-shaped screen or sieve baskets that are 
designed with sortings slots formed between parallel rods. The rods pass 
through supporting rings which hold the rods at the required lateral 
distance. The supporting rings are connected by spacers, which ensure that 
the shape of the screen basket is maintained, even if the rods that define 
the sorting slot are removed. This type of design, however, does not 
produce adequate stability in all cases. 
EP 0 719 890 A2 describes another rod wire or screen device. There, the 
rods are designed to increase in thickness so that they maintain the 
distance necessary for forming the slot. Even if the wires produced by 
this method offer the advantage of easy dismantling, the production of 
these rods is relatively costly. Further, it is difficult to guarantee 
adequate stability with this type of wire. 
SUMMARY OF THE INVENTION 
The object of the present invention is to achieve a screen device with 
optimal stability that is easy to produce. 
This object is achieved by a device including slot-shaped openings for 
sorting fiber suspensions. The device further includes parallel aligned 
rods, forming the sorting slots or slits. The rods are fixed in the 
supporting elements and cover elements. The supporting elements include 
recesses to accommodate, at least partially, the rods, and to connect 
several or all of the rods contained in the screen device. 
The inventive design of the present screen device is advantageous because 
the rods forming the wire slot, and the supporting elements that support 
the rods, are subjected to much less mechanical stress than in the prior 
art. As explained above, depending on the application, considerable 
forces, even pulsations, may occur with this type of screen, that severely 
stress the entire device and eventually may cause its destruction. In the 
immediate vicinity of the slot, moreover, there should be as few 
components as possible, because the components interfere with the flow 
during operation. Due to the inventive design of the present invention, 
the aforementioned forces are only negligibly absorbed by the rods or the 
supporting elements. Rather, the forces are largely transferred to the 
carriers. The carriers may be correspondingly solid, that is to say, 
resistant to bending. Further, in special designs, the longitudinal 
direction of the carriers may have a varying stiffness or thickness 
depending, for example, on the transverse beam calculation. If desired, 
the rods may be held securely in the supporting elements, completely 
without undetachable connections. This is significant, in particular, if 
vibrations create a risk that cracks may form, e.g., on weld seams or the 
like. 
If the screen devices are produced by a method such as, for example, the 
one described in DE 39 27 748 A1, in which the rods are clamped into the 
supporting elements by slightly distorting or deforming the supporting 
elements. Moreover, using relatively narrow supporting elements offers the 
advantage of making it considerably easier to perform the deformation or 
distortion. 
In a further inventive improvement, it is possible to detachably connect at 
least one of the cover elements with the carriers. The cover element may 
be detached or removed for repair purposes. If the seat of the rods in the 
supporting elements is designed correspondingly, the rods may be removed 
for dismantling, e.g., in the longitudinal direction. Clearly, this design 
makes it very easy not only to dismantle, but also to produce special 
screen (or sieve) baskets, because the rods can be inserted. The cover 
elements then prevent the rods from sliding in the axial direction. This 
enables slight prestressing of the rods in the supporting elements, to 
protect the rods against vibrations in the recesses. Such a prestressing 
may be performed by a thermal shrink fitting. 
Fixing the rods in the supporting elements can also be improved upon as 
follows. While assembling the screen or sieve device, the cover elements 
may be connected with the carriers such that the recesses are displaced in 
the direction of the circumference relative to the recesses of the 
supporting elements. As a result, a torsioned strain would be transferred 
onto the rods, which would improve the fixing or setting of said rods. 
The above-described designs, which considerably facilitate the assembly and 
disassembly of individual rods, do not necessarily have to be realized in 
the development of the present invention. The advantages which were 
described initially, and which relate to increasing the stability of the 
screen device, may be enhanced in other cases, for example, where the rods 
in the supporting elements are more or less permanent or undetachable, due 
to soldering, high-temperature soldering, adhesion, or the like. 
Another way to state the invention is a screen device for sorting fiber 
suspensions that includes substantially parallel aligned rods that have a 
longitudinal axis. The device further includes supporting elements that 
include recesses to receive at least part of at least a plurality of the 
rods. The device further includes sorting slots, defined by the rods, and 
cover elements. The rods are coupled with the supporting elements and with 
the cover elements. The supporting elements, moreover, are coupled to the 
carriers on a side opposite a side the supporting elements are coupled to 
the rods. The carriers include faces, which are coupled to the cover 
elements. 
According to another aspect of the invention, the carriers are more rigid 
than the supporting elements. 
According to another aspect of the invention, at least one of the 
supporting elements is permanently affixed to the carriers. Further, it is 
possible for at least one of the cover elements to be detachably connected 
to the carriers. In fact, at least one of the cover elements may be bolted 
onto the carriers. 
According to yet another aspect of the invention, at least one of the cover 
elements may lock the rods against longitudinal movement. Further, it is 
possible that at least one cover element may include recesses to receive 
at least part of the rods. 
According to still yet another aspect of the invention, at least one cover 
element may brace the rods. 
According to another aspect of the invention, the device may further 
include at least one spring element that is positioned between at least 
one of the rods and at least one of the cover elements. Further, it is 
possible for the spring element to be composed of a seal. 
According to another aspect of the invention, at least one cover element 
may includes recesses and the cover element may be positioned to 
circumferentially displace the cover element recesses relative to the 
supporting element recesses. Thus, the rods are deformably positioned 
within the cover element recesses. 
According to another aspect of the invention, the rods may be impermanently 
attached such that the rods are immovable during use of the screen device. 
According to another aspect of the invention, the rods may be removable, in 
the direction of the longitudinal axis of the rods, from the supporting 
elements, after at least one cover element is removed. 
It is possible for the rods being permanently affixed to the supporting 
elements. 
According to another aspect of the invention, the recesses in the 
supporting elements may be beveled towards the inside and expand further 
deeper inside. 
Further, it is possible for the sorting slots to be further defined by the 
supporting elements. 
According to yet another aspect of the invention, the rods may be composed 
such that they increase in thickness where the rods are received by the 
supporting elements. Further, the rods may have a cross section that is 
shaped like a triangle with rounded-off edges at the point where the rods 
are received by the supporting element. 
According to another aspect of the invention, the rods may be formed of a 
drawn profile. 
Further, according to another aspect of the invention, the supporting 
elements and the cover elements may be ring-shaped, wherein the screen 
device is a cylindrical screen basket. 
It is possible, moreover, for the supporting elements and the cover 
elements to be annular segments, so that the screen device is a curved 
screen or so that the screen device is a semi-circular screen basket. 
According to another aspect of the invention, it is possible to have a 
screen device that is not circular or curved. Rather, the rods may be 
arranged in a substantially flat plane. 
Further, it is possible to have the supporting elements to be positioned 
perpendicular, or substantially perpendicular, to the rods and be coupled 
with the rods in that manner. 
According to yet another aspect of the invention, the carriers may be 
arranged such that the carriers are in plane that is substantially 
parallel to the plane in which the rods are arranged. In this case, the 
screen extends in a substantially linear direction, i.e, is flat or 
planar. 
Another way to explain the invention is as a screen device for sorting 
fiber suspensions that includes rods including top faces and bottom faces. 
The rods have a longitudinal axis and are positioned substantially 
parallel to the longitudinal axis to form slits. The device further 
includes support elements, having a rod receiving side that includes 
recesses, a top cover element covering the top faces of the rods and a 
bottom cover element to cover the bottom faces of the rods. The device 
further includes carriers associated with the top cover element and the 
bottom cover element. The support elements are connected to the carriers 
on a side opposite the rod receiving side. 
According to another aspect of the invention, the top cover element may be 
impermanently attached to the top faces of the rods. Further, the top 
cover element may be impermanently attached to the top faces of the rods, 
and the bottom cover element may be impermanently attached to the bottom 
faces of the rods. 
According to another aspect of the invention the rods may be positioned on 
the outer side of the support elements. Further, the rods may be 
positioned on the inner side of the support elements. 
According to another aspect of the invention, the bottom cover may be 
permanently attached to the bottom faces of the rods. 
According to another aspect of the invention, the device may further 
include at least one spring element adjacent the top faces of the rods and 
adjacent the top cover element. Further, at least one spring element may 
be adjacent the bottom faces of the rods and adjacent the bottom cover 
element. 
It is possible for the carriers to be composed of a steel profile with a 
substantially rectangular cross section. 
Other exemplary embodiments and advantages of the present invention may be 
ascertained by reviewing the present disclosure and the accompanying 
drawing.

DETAILED DESCRIPTION OF THE PRESENT INVENTION 
The particulars shown herein are by way of example and for purposes of 
illustrative discussion of the preferred embodiments of the present 
invention only and are presented in the cause of providing what is 
believed to be the most useful and readily understood description of the 
principles and conceptual aspects of the invention. In this regard, no 
attempt is made to show structural details of the invention in more detail 
than is necessary for the fundamental understanding of the invention, the 
description taken with the drawing figures making apparent to those 
skilled in the art how the invention may be embodied in practice. 
FIG. 1 is a cross-section view of a screen or sieve device. It shows one of 
the parallel aligned rods 3 held by a multitude of supporting elements 1. 
According to the invention, the supporting elements 1 are connected to the 
carriers 5 on the side of the supporting elements 1 that is opposite the 
rods 3, (i.e., in FIG. 1, on the left-hand side). The carriers 5, in turn, 
are connected to the cover elements 2. Here, the carrier 5 is composed of 
a steel profile with a rectangular cross section that is not equal in 
length (i.e., transverse beam calculation), so that the carrier 5 better 
absorbs the bending forces across the length of the carrier 5. In the 
region of the face, the carrier is connected on both sides with the cover 
elements 2. This connection may be performed both on the face and in the 
area near the face. In the example shown in FIG. 1, the lower cover 
element 2 is more or less permanently connected (for example, by welding) 
with the carriers 5 so that it is undetachable. On the other hand, the 
upper cover element 2 can be removed if required, because this element is 
screwed onto the carriers 5. As previously discussed, this enables the 
screen device to be easily dismantled, as for example, removing the rods 3 
in the longitudinal direction. The screen device shown in this example is 
substantially cylindrical. For this reason, the cover elements 2 and the 
supporting elements 1 are substantially annular. To present a clearer 
picture, FIG. 1 shows only rod 3, and the supporting elements are merely 
sketched, i.e., their annular shape is not shown. 
FIG. 2 is a cross-sectional top view of the screen device. The drawing 
shows four rods 3 with recesses 6 in the supporting elements 1. In this 
drawing, four rods 3 are visible, and in other places the recesses 6 are 
shown. The recesses 6 are incorporated in the supporting elements 1. The 
supporting element 1 rests against the carrier 5 which, in turn, is 
connected with the subjacent cover element 2. Further, FIG. 2 indicates a 
weld seam between the carrier 5 and the cover element 2. 
The cover elements 2 (in FIG. 1) may transmit an axial force to the rods 3 
through the spring elements 7 that are respectively located at the face of 
the rods 3. The spring elements 7 may either be circular sealing rings or, 
as is indicated in FIG. 5, if the cover elements 2 includes recesses 6' 
for a precision-fit accommodation of three rods 3, the inserted spring 
elements 7 will have a corresponding shape. In such cases, the cover 
element 2, for all practical purposes, is closely connected to the 
carriers 5. Further, the spring elements 7 are advantageous in that they 
act as a seal. 
FIG. 3 shows a different method of attachment, wherein the cover element 2 
is placed directly on the rods 3, and the screw connection between the 
cover element 2 and the carrier 5 is composed of a clamping connection 
with the slot. This enables an adjustable fixing force to be provided. 
Where it is not required to dismantle the rods 3, both cover elements 2 can 
be more or less permanently connected with the carriers 5, so that they 
are undetachable. For example, the cover elements 2 and the carriers 5 may 
be welded, as shown in FIG. 4. FIG. 4 also shows the possibility of 
placing the carriers 5 radially towards the inside. This is appropriate if 
the rakers for the screen device move outward, i.e., radially beyond the 
rods 3. For practical purposes, in the other examples shown here, the 
rakers move inside. 
FIGS. 3 and 4 show another variation wherein the rods 3 are pushed through 
the supporting elements 1. Thus, the rods 3 may be removed only in the 
longitudinal direction. In FIG. 1, the rods 3 are only partially enclosed 
by the supporting elements 1. 
In FIG. 2, the rods are shown with a special profile. This profile is 
particularly advantageous for fixing or assembling the rods 3 in the 
supporting elements 1 because the supporting elements 1 are flexible, so 
that the deformation or distortion of the supporting elements 1 allows the 
rods 3 to be assembled or fixed. 
While in many cases it is appropriate to provide the carriers with an 
uneven cross section, another design can be provided. As shown in FIG. 5, 
the carriers have a substantially constant carrier profile. Of course, the 
profile does not necessarily have to be rectangular. 
FIG. 6 shows a perspective view of the complete screen or sieve device 
according to the invention, in which some of the carriers 5, in this case, 
three (only two of which are shown), support the supporting elements and 
are fixed in the cover elements 2. Screw connections are indicated on the 
upper cover element 2. As is known, this type of screen device includes a 
large number of rods 3, of which only a few are shown. 
FIG. 7 depicts another possible embodiment of the present invention. In 
FIG. 7, the rods 3 are presented in a substantially flat plane, that is, 
the rods do not form a semi-circle or cylindrical basket. Rather, the rods 
3 are assembled to form a substantially flat screen device. As shown in 
FIG. 7, when the rods 3 are assembled in this manner, the carriers 5 may 
also be formed in a substantially flat plane. In fact, the plane in which 
the carriers 5 are formed may be substantially parallel to the plane in 
which the rods are assembled. The supporting elements 1 are coupled with 
the rods 3 and the carriers 5. 
It is noted that the foregoing examples have been provided merely for the 
purpose of explanation and are in no way to be construed as limiting of 
the present invention. While the invention has been described with 
reference to a preferred embodiment, it is understood that the words which 
have been used herein are words of description and illustration, rather 
than words of limitation. Changes may be made, within the purview of the 
appended claims, as presently stated and as amended, without departing 
from the scope and the spirit of the invention in its aspects. Although 
the invention has been described herein with reference to particular 
means, materials and embodiments, the invention is not intended to be 
limited to the particulars disclosed herein; rather, the invention extends 
to all functionally equivalent structures, methods and uses, such as are 
within the scope of the appended claims.