Interlocking screen elements

A sieve screen module comprises a plurality of screen elements whose opposed edges contain complementary formations interlocked by an elongate member fixedly secured in the formation by a settable material. A number of modules may be assembled by passing a rod thru the elongate member.

This invention relates to screening, and in particular to sieve screens 
produced by connecting together a plurality of sieve elements. Such 
screens are used in screening machines for dewatering, grading and the 
like. 
It is known to cast an individual sieve element in a standard size as a 
mesh of polymeric material having apertures of a required shape and size. 
The mesh is often reinforced by the incorporation of inelastic material 
during casting. 
A plurality of such sieve elements are then bonded together to provide a 
sieve screen of desired overall dimensions which is then fitted over a 
support frame in the screening machine. 
According to the present invention a method of making at least part of a 
sieve screen includes the step of interlocking a plurality of sieve 
elements with complementary formations of adjacent elements engaging and 
defining an open-sided channel receiving an elongate interlocking member, 
which member is then secured against relative lateral movement of the 
screen elements. 
Preferably the elements are interlocked by a rigid member such as a rod, 
tube, wire or the like extending through or into the engaged formations. 
According to another aspect of the invention a sieve screen part is made by 
the method of the first aspect and comprises a plurality of interlocked 
sieve elements with complementary formations of adjacent elements engaging 
and interlocked. 
In preferred embodiments the formations are adapted to engage with those of 
an adjacent sieve element and define the channel to receive an 
interlocking member and be filled with settable material to provide a 
substantially smooth continuous surface for the joint between the 
elements. 
The interlocking prevents relative lateral movement of the elements i.e. in 
the plane of the sieve screen and, each sieve element includes an 
apertured body portion, the complementary formations comprising extension 
pieces from the edges thereof. 
In one embodiment of the invention, the sieve elements include apertured 
body portions, the complementary formations comprising extension pieces at 
the edges to be engaged and of less thickness than the elements. The 
extensions serve to space the sieve elements to provide the channel 
therebetween, and may further be provided with means, such as depending 
limbs, for engaging the interlocking member to provide a mechanical 
interlocking effect. 
In one method of embodying the invention the interlocking member is secured 
by introducing into the cavity a settable material e.g. liquid polymeric 
material or other adhesive. This material may fill the cavity and may also 
enclose substantially the whole length of the member, but leaving the ends 
accessible. 
When the liquid polymeric material sets the sieve elements are secured to 
each other and/or the interlocking member by mechanical interlocking 
and/or adhesion. 
When a desired number of sieve elements have been joined together in this 
way to produce a sieve screen part or module of a desired length, a sieve 
screen, flat or curved, of a desired width may be provided by joining a 
plurality of parts or modules by a rod or rods of metal or the like which 
extends through corresponding tubes in adjacent modules. The rods may be 
provided with means for securing them to the structure of a screening 
machine. 
Stiffening members may be provided between adjacent modules, preferably in 
the form of strips having slots spaced at intervals corresponding to the 
rods. The strips are fitted onto the rods between adjacent sieve modules 
after the modules have been located on the rods. 
The modules may be clamped together by fixing bars, similar to the 
stiffeners, extending along the ends of the rods and secured thereto, for 
example by screws or welding. 
Where a sieve screen is to be tensioned when in position in the screening 
machine, a filamentary member such as a flexible cord or the like may be 
used instead of a rod. The flexible cord need not be secured to the fixing 
bar of the end module but would be provided at its ends with means for 
securing it to conventional tensioning and/or clamping means of the 
screening machine. 
Other aspects of the invention comprise a sieve screen at least part of 
which is made by one of the foregoing methods, sieve screen elements for 
use in the foregoing method and a screening machine including such a sieve 
screen.

Where corresponding parts are shown in different Figures they are given the 
same reference numeral. 
Referring to FIGS. 1, 2 and 3, sieve elements 10 include rectangular 
parallelepiped body portions 11 which have apertures therethrough to 
provide in each a mesh 12. Opposed edges of the body portions have surface 
extension pieces 13, castellated as shown in FIG. 3. The castellations are 
dimensioned so that when two similar elements are juxtaposed the extension 
pieces interlace to provide a substantially smooth continuous surface for 
the joint between them. The extension pieces are of lesser thickness than 
the body portion and serve to space the juxtaposed elements to leave a 
channel 16 therebetween (FIG. 2). 
When making a sieve-screen module, a plurality of sieve elements are 
juxtaposed with their extension pieces interlaced, a tube 17 is laid in 
the channel to extend across the extension pieces, and the channel filled 
with liquid polymer 18. When the polymer sets the elements are bonded 
securely together. 
Mechanical interlocking of the elements with the tube is provided by limbs 
19 which depend from, and are integral with, respective ends of extension 
pieces 13 of the sieve elements. 
FIGS. 4 and 5 show sieve screen modules 21, produced as described above, 
arranged for assembly together to form a sieve screen. Metal rods 22 
extend through corresponding tubes of adjacent modules 21. Stiffeners 23, 
in the form of elongate strips of rectangular cross-section are located 
between the modules, the rods passing through slots 28 in the strips. 
When the desired number of modules have been assembled onto the rods, 
fixing bars 24, similar to the stiffeners, are positioned across the edges 
of the modules adjacent to the ends of the rods, and are welded to the 
rods as indicated at 25. Other means of securing the fixing bars to the 
rods could be used, for example screws. 
A sieve screen made in the aforesaid way may be flat or curved, and the 
tubes may be rigid or flexible. 
An advantage of the above embodiments is that the complementary formations 
of adjacent elements provide for a secure, substantially aperture-free 
joint between the screen elements whilst wasting little of the useful 
sieve area of the screen. 
Where a sieve screen is to be tensioned, a flexible cord 30 may replace 
each rod 22. A modified fixing bar is used in combination with the 
flexible cord and is illustrated in FIGS. 6 and 7. The flexible cord 30 
extends through a flexible tube 17 embedded in the joint between sieve 
elements 10 and has an enlarged head portion 31. The fixing bar includes 
an apertured plate portion 32 through which the cord extends and which is 
clamped by the enlarged head portion 31 against the edges of the sieve 
elements 10. Integral with the plate 32 and extending away from the plate 
and sieve element is a hooked portion 33 of the fixing bar. This hooked 
portion is adapted to engage with the conventional clamping and tensioning 
means provided in the screening machine. 
An advantage of a sieve screen being tensioned in this way is that 
elongation or other deformation of the sieve apertures is avoided since 
the tensioning force is not applied directly across the sieve elements. 
It will be appreciated that the invention affords practical advantage in 
the construction and/or maintenance of sieve screens. During construction, 
virtually any desired sieve dimension can be obtained by suitable choice 
of modules and elements. During maintenance, individual modules or 
elements can be replaced quickly and easily by removing the fixing bars, 
dissembling the modules from the rods, substituting modules as required, 
and reassembling as per the foregoing description. 
The sieve elements described could be metal, synthetic plastics or a 
combination of both. For example, synthetic plastics material could be 
formed around a metal grid-like skeletal support structure. Extension 
pieces and outer covering of the grid would then be of synthetic plastics 
material having a long life compared to, say, mild steel, from which the 
grid could be made. Alternatively, the extension pieces could be of metal 
with a synthetic plastics material sieve insert. 
A suitable synthetic plastics material having good wear characteristics in 
polyurethane. 
The individual sieve elements may conveniently be injection moulded. 
In the foregoing description the individual sieve elements 10 are of a flat 
rectangular shape, but embodiments of the invention comprehend other 
shapes, for example tapered and/or curved, especially where the screen is 
for use as a centrifuge basket. 
FIG. 8 shows, in plan, an element 10 having castellated formations 13 
engaging interlocking members 22 in the usual way, but having its other 
sides 31 converging, there being a correspondingly lesser number of 
castellations at one end of the element than at the other. 
It will be appreciated that where the element is both tapered and curved, a 
plurality of elements connected together will form a conical screen.