U.S. patent number 3,833,120 [Application Number 05/280,946] was granted by the patent office on 1974-09-03 for rubber screen for a vibrating sieve.
Invention is credited to Nobuo Ogata.
United States Patent |
3,833,120 |
Ogata |
September 3, 1974 |
RUBBER SCREEN FOR A VIBRATING SIEVE
Abstract
A rubber screen for use in a vibrating sieve for separating
smaller particles of a substance from larger particles thereof,
which screen comprises a body having a plurality of apertures and
containing reinforcing members embedded therein and oriented
laterally to the flow direction of the substance being sifted. An
abrasion-resistive coating may be applied to one or both surfaces
of the rubber screen.
Inventors: |
Ogata; Nobuo (Kamakura City,
JA) |
Family
ID: |
26711215 |
Appl.
No.: |
05/280,946 |
Filed: |
August 16, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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34654 |
May 5, 1970 |
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Current U.S.
Class: |
209/399 |
Current CPC
Class: |
B07B
1/46 (20130101) |
Current International
Class: |
B07B
1/46 (20060101); B07b 001/46 () |
Field of
Search: |
;209/392-403 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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108,053 |
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Jul 1937 |
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AU |
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6,715,196 |
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May 1968 |
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NL |
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1,197,310 |
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Jul 1965 |
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DT |
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Primary Examiner: Lutter; Frank W.
Assistant Examiner: Hill; Ralph J.
Attorney, Agent or Firm: Fleit, Gipple & Jacobson
Parent Case Text
This is a continuation-in-part application of application Ser. No.
34,654 filed May 5, 1970, now abandoned.
Claims
What is claimed is:
1. A rubber screen for use in a vibration sieve for separating
smaller particles of a substance being sifted from larger particles
thereof while passing said substance along the top surface of the
rubber screen, comprising a planar body made of rubber-like
resilient material and having a plurality of apertures bored
therethrough for passing the smaller particles, a pair of mounting
members integrally formed on opposite edges of the planar body, and
elongated inextensible members made of flexible cords and embedded
in the screen so as to extend between said opposite edges of the
screen, each of said elongated inextensible members being
continuous members tautly extending across the entire width of the
planar body and across said opposite edges at right angles thereto,
said mounting members including bent end portions of the continuous
members, said mounting members further including stopper plates
having small apertures and stopper pins, each of the continuous
elongated inextensible members having end portions thereof so bent
as to form a folded loop-like end portion, each said stopper pin
extending through said loop-like end portion of the elongated
inextensible member at an outer surface of the stopper plate
relative to space between said opposite edges, the stopper plates
thus coupled to the end portions of the elongated inextensible
members being embedded in the rubber screen along opposite edges of
the rubber screen.
2. A rubber screen for use in a vibration sieve for separating
smaller particles of a substance being sifted from larger particles
thereof while passing said substance along the top surface of the
rubber screen, comprising a planar body made of rubber-like
resilient material and having a plurality of apertures bored
therethrough for passing the smaller particles, elongated flexible
inextensible members embedded in the screen so as to extend between
opposite edges of the screen, each of said elongated inextensible
members having opposite ends thereof terminated in means for
mounting said screen and allowing tensioning of said elongated
inextensible members, and adjacent ones of said elongated
inextensible members having a plurality of said apertures
therebetween.
3. A rubber screen according to claim 2 further comprising cores in
each of said mounting means, and wherein said elongated
inextensible members are bent around said cores.
4. A rubber screen according to claim 3 wherein a plurality of said
cores are provided in each opposite edge of the planar body, and
wherein said mounting means are provided on said opposite edges
only in the regions of said cores.
5. A rubber screen according to claim 2, wherein said inextensible
members are continuous members extending across the entire width of
the planar body and across said opposite edges at right angles
thereto, said mounting means including bent end portions of the
continuous members.
6. A rubber screen according to claim 5, wherein the continuous
members are made of a material selected from the group consisting
of steel ropes, steel wires, steel members, and fibrous cords.
7. A rubber screen according to claim 5, wherein the continuous
members include at least two continuous members disposed along the
opposite edges of the screen at right angles to said opposite edges
of the rubber screen.
8. A rubber screen according to claim 5, wherein one set of the
opposite edges of the rubber screen is bent upwards above the upper
surface of the remaining portion of the rubber screen, so as to
form said mounting means.
9. A rubber screen according to claim 5 and further comprising a
pair of grooves formed on the upper surface thereof along one set
of the opposing edges thereof, so as to constitute said mounting
means.
Description
This invention relates to a rubber sieve, and more particularly to
a rubber screen for a vibrating sieve to be used in ore-dressing
plants of various mines and steel mills. The present invention is
directed to an improvement of a rubber screen to be used as a
horizontal or inclined mesh in a vibrating sieve device through
which the finer particles of a pulverized or granulated substance
are passed to separate them from the coarser particles. The rubber
screen may consist of any suitable rubber-like resilient
material.
A metallic wire screen has heretofore been used as the mesh element
of a vibrating sieve device. Such metallic wire screen has
shortcomings in that it generates considerable noise during
operation, its service-life is comparatively short due to its
wearing, it rusts, and the mesh becomes clogged.
To mitigate such difficulties of known metallic wire screens, it
has been proposed to use a rubber screen consisting of rubber-like
resilient material. Known rubber screens, however, are susceptible
to vibration of large amplitude, which cause various inconveniences
in practical operations.
Therefore, an object of the present invention is to obviate such
difficulties of known metallic wire screens and rubber screens, by
providing an improved rubber screen which is free from any of such
difficulties.
For a better understanding of the invention, reference is made to
the accompanying drawings, in which:
FIG. 1 is a perspective view of a known vibrating sieve using a
metallic wire screen;
FIG. 2 is a vertical cross section of the vibrating sieve of FIG.
1, taken at right angles to the direction of the flow of material
being sifted thereby;
FIG. 3 is a perspective view of the wire screen in the vibrating
sieve;
FIG. 4 is a vertical sectional view of a known vibrating sieve
using a rubber screen, taken at right angles to the direction of
the flow of material being sifted thereby;
FIG. 5a is an enlarged fragmentary sectional view of a joint
portion of the rubber screen of the device of FIG. 4, taken along
the flowing direction of the material being sifted thereby;
FIG. 5b is a view showing the details of the joint portion;
FIGS. 6a, 6b, and 6c are plan views of different rubber screens,
according to the present invention;
FIG. 7a is a vertical sectional view of a rubber screen according
to the present invention, taken at right angles to the direction of
the flow of material being sifted thereby;
FIGS. 7b to 7f are enlarged fragmentary sectional views,
illustrating different constructions of the mounting portion of a
rubber screen of the present invention;
FIG. 8 is a perspective view of a vibrating sieve incorporating a
rubber screen, according to the present invention;
FIG. 9a is a partial enlarged sectional view of one of the joint
portions of a rubber screen according to the present invention,
taken along the flow direction of the material being sifted
thereby; and
FIG. 9b is an enlarged fragmentary sectional view of the joint
portion.
Like parts are designated by like numerals throughout the
drawings.
In a known vibrating sieve with a metallic wire screen, as shown in
FIG. 1, the metallic wire screen 1 with crossing metallic wires is
supported by a number of longitudinal frame members 3 carried by
lateral frame members 2. The "longitudinal" direction is parallel
to the flow direction of the material being sifted by the sieve, as
shown by the arrow A of FIG. 1, while the "lateral" direction is
perpendicular to the flow direction Side edges 1' of the metallic
wire screen 1, as shown in FIG. 3, are bent along the lower edge of
each clamping bar 4, as best can be seen from FIG. 2. The clamping
bars 4 are then fastened to two side walls 9, respectively, by
means of bolts 5 and nuts 6. A holding bar 11 is disposed on the
screen 1 along the central axis thereof, which holding bar 11 is
secured to the central member 3' of the longitudinal frame members
3 by a suitable fastening means 10, so as to securely hold the
screen 1 on the frame members. In the illustrated example, the
fastening means 10 includes stud bolts projecting from the central
longitudinal frame member 3' and nuts engaging the stud bolts,
respectively. Retaining bars 7 are integrally formed on the side
plates 9, for preventing the clamping bars 4 from slipping along
the side plates during the vibration. Each side plate 9 includes a
suitable ledge 8 for stably supporting the longitudinal side edge
of the screen 1, which ledge may be made by an angle steel.
The metallic wire screen 1 in such vibrating sieve produces noise
of considerably high level during the sifting operation. Besides,
individual metallic wires forming the screen 1 wear fairly quickly,
if the screen is used for sifting hard particles or granules of
ore, resulting in a short service life. It is susceptible to rust
or corrosion, as well as clogging, which also lead to short service
life.
In order to mitigate such difficulties of the known metallic wire
screen, it has been proposed to use a rubber screen made of rubber
or rubber-like resilient material. FIG. 4 illustrates a vibrating
sieve using a rubber screen of known construction. In the figure, a
rubber screen 12 comprises a rubber sheet with a plurality of
apertures 13, through which fine particles to be sifted fall down.
Ribs r are integrally formed at the opposite edges of the screen 12
extending in parallel with the flow direction of material, being
sifted, to facilitate the mounting of the screen to the side plates
9 by means of clamping bars 4. A suitable tension is preferably
applied to the screen 12 when it is mounted on the sieve. In
operation, a pulverized or granulated material to be sifted is fed
onto the rubber screen 12, while vertically reciprocating or
vibrating the screen (e.g., along a circular or elliptic path,
two-dimensionally or three-dimensionally), so that fine particles
with a diameter smaller than that of the aperture 13 fall through
the apertures 13. Thus, the finer particles of the substance thus
fed are separated from coarser particles.
The known rubber screen, however, has the following drawbacks.
During the sifting operation, the rubber screen 12 itself vibrates
while forming nodes at the clamping bars 4 and a holding bar 11.
Such vibration of the rubber screen 12 is shown by two-dot-dash
lines in FIG. 4. The amplitude of such vibration of the rubber
screen can become very large under certain conditions. If a light
substance with a comparatively small specific gravity, e.g., coke
particles, is sifted by such sieve, light particles of the
substance are apt to be thrown out of the screen over the side
plates 9. In practice, additional holding bars 14 are secured to
longitudinal frame members 3, so as to suppress the amplitude of
such vibration of the rubber screen per se, by fastening the rubber
screen to the frame members not only at the central portion thereof
but also at other intermediate positions, as shown in FIG. 4. The
additional holding bars 14, however, reduce the effective surface
area of the rubber screen 12 to lessen the sifting efficiency. The
use of the additional parts inevitably increases the cost of the
sieve device, and requires extra man-hours for replacement of the
rubber screen in case of any breakage in the rubber screen.
Accordingly, the use of such additional holding bars 14 is not
preferable.
If no extra holding bars 14 are added, the pulverized or granulated
substance flowing on the rubber screen tends to concentrate in
spaces between adjacent longitudinal frame members 3, inclusive of
the central member 3'. If the substance being sifted has a
comparatively large specific gravity, such flow of the substance on
the screen tends to cause a considerably large tension in the
rubber screen at such portions where it engages frame members 3 and
3'. As a result, the wear of the rubber screen is accelerated at
such portions by the tension thus generated, and the rubber screen
12 is often torn out at such portions.
Sometimes, it is desirable to have a long sieve. To this end, a
desired elongated sieve is preferably made by connecting a number
of comparatively short rubber screen units, because partial
replacement is easier than the total replacement of a long unitary
screen in the case of breakage. With conventional rubber screens,
the joint portion of short screen units for producing such long
screen is made by overlaying the edge portions of the adjacent
short screen units, as shown in FIGS. 5a and 5b. Accordingly, there
are formed a number of bumps Q on the sifting surface of the long
rubber screen. The bumps Q not only disturb the smooth flow of
substance being sifted to hamper the sifting efficiency, but also
cause the particles of the substance to strike such bumps to
increase the wear of the rubber screen. As a matter of fact, such
long rubber screen is often broken at such joint portions.
Therefore, an object of the present invention is to obviate the
aforesaid difficulties of known metallic wire screens and the known
rubber screens by providing an improved rubber screen.
FIG. 6a shows an embodiment of the rubber screen, according to the
present invention. A rubber screen 12 of the present invention
includes a plurality of inextensible, flexible and continuous
reinforcing members 15 completely buried therein, which reinforcing
members extend at right angles to the flow direction A of the
substance being sifted thereby and which members 15 are placed
under tension. In the embodiment of FIG. 6a, the flexible
reinforcing member 15 under tension are buried at or in the
proximity of the opposite edges e, e' of the rubber screen, lateral
to the flow direction A, and at the suitable portions between the
edges e and e'. The reinforcing members can be made of any suitable
flexible and inextensible material, such as steel ropes, steel
wires, steel members, other organic or inorganic cords, and the
like. Although the reinforcing members 15 in the embodiment of FIG.
6a are disposed at right angles to the flow direction A of the
substance being sifted, the invention is not restricted to such
disposition. In fact, any suitable disposition of the reinforcing
members 15 is possible relative to the flow direction A, for
instance, at a slanted relation to the flow direction A. A
plurality of screening apertures 13 are bored through the rubber
screen 12, but such apertures are not provided where the
reinforcing members 15 are buried.
Opposing end portions 16 (FIG. 7) of each reinforcing member 15
extend sideways from the side edges of the sifting portion of the
rubber screen 12, to form ribs r and r'. The ribs r, r' thus
extended can be bent along the lower edges of the clamping bars 4,
as described hereinbefore referring to the metallic wire screen 1
of FIG. 1. The rib r or r' thus formed may be provided with a
rubber coating, as shown in FIG. 7c. Alternatively, each end
portion 16 of the reinforcing member 15 can be looped, so as to
surround a holding core 17 for constructing a solid rib r or r', as
shown in FIGS. 7a and 7b. To strengthen the rib portions, it is
possible to fasten the core 17 to the reinforcing members 15 by
suitable bolts or fasteners (not shown).
In the preferred embodiment of FIGS. 6a, the holding cores 17
extend in parallel to the flow direction A along the opposing edges
of the screen 12, so as to connect the reinforcing member 15 in the
rubber screen 12 by means of the ribs r and r', which ribs extend
integrally with the cores 17 over the full length of the rubber
screen. It is possible to use short holding cores 17 at each end
portion 16 of the individual reinforcing member 15, so as to form a
separate rib r or r' at each end of the reinforcing member 15, as
shown in FIG. 6b.
The rib portions r and r' are used to securely hold the rubber
screen 12 to the side plates 9 by means of the clamping bars 4, as
shown in FIG. 8. It should be understood that the ribs r and r'
need not extend upwards in excess of the plane of the upper surface
of the rubber screen 12. In fact, the top of the ribs r and r' can
be flush with the top surface of the rubber screen 12, while
forming longitudinal grooves 18 thereon, as shown in FIG. 7d. The
longitudinal grooves 18 engage the lower edges of the corresponding
clamping bars 4 for securely fastening the rubber screen 12 to the
side plates 9.
FIGS. 7e and 7f illustrate another embodiment of the termination of
flexible reinforcing members 15. The end portion 16 of each
reinforcing member 15 is turned back so as to form a folded
portion, as shown in FIG. 7e. The folded end portion of the
reinforcing member 15 is inserted into a coacting aperture bored
through a stopper plate 15a, so as to project the folded edge
portion of the rienforcing member 15 slightly beyond the outer
surface of the stopper plate, as shown in FIG. 7e. A stopper pin
15b is forced into a closed loop defined by the folded portion of
the reinforcing member 15 and the stopper plate 15a. The size of
the opening of the stopper plate 15 and the dimensions of the
stopper pin 5b are such that, once the end assembly of the
reinforcing member 15 thus fabricated is enclosed in the form of a
rib r or r' by the rubber material of the rubber screen 12, as
shown in FIG. 7e, the stopper plate 15a is integrally secured to
the reinforcing member 15. Thus, the stopper plate 15a holds the
reinforcing member 15 against a tension tending to pull the
reinforcing member 15 away from the stopper plate 15 in a direction
as shown by the arrow F of FIG. 7e. The embodiment of FIGS. 7e and
7f is particularly suitable for the reinforcing member 15 in the
form of a strap.
With the construction of the ribs r and r', as shown in any one of
FIGS. 7a to 7f, the flexible reinforcing members 15 buried in the
rubber screen 12 can be tightly secured to the side plates 9, by
means of the clamping bars 5 and the fastening means consisting of
bolts 5 and nuts 6. If the length of each reinforcing member 15 is
suitably determined, relative to the spacing between the side
plates 9 of the sieve structure, it is possible to apply a proper
tension to the reinforcing members 15 when they are fastened to the
sieve. The direction of such tension applied to the reinforcing
members 15 is apparently substantially lateral to the flow
direction A, as long as the members 15 are disposed in the manner
as shown in FIGS. 6a and 6b.
According to the present invention, instead of using the aforesaid
continuous reinforcing members 15 buried in the rubber screen, it
is also possible to fulfill the object of the invention by using a
rubber screen 12 made of a compound rubber material, such as
fiber-reinforced rubber, which consists of rubber material and
short fibers mixed therein. More particularly, 5 to 50 percent by
volume of short fibers 15' of which length is about 5 mm to 50 mm
are added to the rubber material, based on the total volume of the
rubber screen, and the short fibers are oriented lateral to or at
right angles to the flow direction A of the substance being sifted,
as illustrated in FIG. 6c. The short fibers are, for instance,
short metallic pieces, textile cut fibers, short textile yarns,
short cords or organic or inorganic material, or the like. In the
case of the rubber screen using such compound rubber material, the
sectional shape of the rubber screen can be made the same as that
of the rubber screen with the reinforcing members 15, as described
hereinbefore referring to FIGS. 7a to 7d. In order to make such
rubber screen, the compound rubber material containing the
aforesaid amount of short fibers of the said dimension is
thoroughly mixed by a rubber kneading roll, and the short fibers
are oriented to the desired direction.
When the short fibers are added and oriented lateral to the flow
direction A, the rubber screen 12 will have a comparatively high
rigidity in a lateral direction relative to the flow-direction A,
namely in the longitudinal direction of the short fibers 15'. The
degree of the rigidity depends on the amount of the short fibers
15' added in the compound rubber. Accordingly, it is possible to
provide rubber screens 12 having optimal rigidity for specific
applications, such as for sifting light coke particles or heavy
iron ore particles.
The rubber screen 12 made of such compound rubber material can be
mounted on the sieve in the same manner as that of the rubber
screen with the reinforcing members 15, as shown in FIG. 8. The
opposing edges e and e' of the rubber screen 12 made of the
compound rubber, which edges are lateral to the flow direction A of
the material being sifted, are sometimes required to have a higher
rigidity than that of the remaining portion of the rubber screen,
for providing a perfect joint portion between adjacent rubber
screens 12 of such construction. In this case, it is preferable to
embed continuous reinforcing members 15 along the edges e and e',
as shown in FIG. 9b. The material of the reinforcing member along
the edge e or e' can be the same as that for those embedded in the
intermediate portions of the rubber screen 12 without compound
rubber, as described hereinbefore referring to FIGS. 6a and 6c.
Accordingly, with the rubber screen of the present invention, there
will be no vibration of large amplitude in the rubber screen
between the central holding bar and the side plates. The risk of
dropping the particles which are being sifted, over the side
plates, is completely eliminated. Besides, the number of the
holding bars 11 necessary for holding the rubber screen of the
present invention on the sieve can be minimized.
Furthermore, when it is desired to form a long rubber screen by
connecting a plurality of unit screens, the rubber screens of the
present invention are particularly advantageous. Referring to FIGS.
9a and 9b, at the connecting portion b of adjacent rubber screen
units 12, the edges e, e of the abutting rubber screens 12 include
reinforcing members 15 embedded therein, respectively. The abutting
edges are slant cut, as best shown in FIG. 9b, relative to a
vertical plane perpendicular to the flow direction A.
As a result, a smooth continuous surface is made on the long rubber
screen by the connection of a plurality of the rubber screen units
12 of the present invention. Accordingly, bumps at the connecting
portions of the adjacent rubber screen units, which have been
experienced in conventional rubber screen as shown in FIGS. 5a and
5b, can completely be eliminated. Consequently, smooth flow of
pulverized or granulated substance being sifted is ensured, and the
sifting efficiency is considerably improved. The elimination of the
bumps at the connecting portions of the adjacent rubber screen
units results in the complete removal of the striking of the rubber
screen by the substance being sifted, and the degree of the wear
and tear is reduced, so that the service life of the rubber screen
is also greatly improved.
In mounting the rubber screen 12 of the invention, it is preferable
to stretch it in a direction lateral to the flow direction A of the
material being sifted, so as to apply a suitable tension to the
flexible but inextensible reinforcing members 15 or short fibers in
the compound rubber. Such tension acts to reduce the vertical
vibration of the reinforcing members, or the short fibers, at the
longitudinal frame members 3 and 3', and accordingly the tension
suppresses the vertical vibration of the rubber screen 12, so that
elongation of the rubber screen surfaces due to such vertical
vibrations is greatly reduced. As a result, the local wear of the
rubber screen in the proximity of such frame members, which was
experienced with conventional rubber screens, is also substantially
eliminated. Thus, the wearing of the rubber screen becomes uniform
over the entire span thereof. Such elimination of the local wear
also contributes to the improvement of the service life of the
rubber screen.
Still other conventional rubber screens have utilized
reinforcements of inflexible solid rods or bars. The performance
used by the rubber screen of the present invention utilizing
flexible but inextensible reinforcing members or cords 15 under
tension is far superior to that achieved by the use of conventional
rubber screens utilizing inflexible solid rods or bars, such as
taught in Australian Pat. No. 108,053. Conventional rubber screens
using inflexible solid rubber rods or bars as reinforcing members
are frequently troubled by the tendency of the screen to become
clogged. This clogging tendency is avoided by use of the screen of
this invention, since the flexible reinforcing cords may flex when
one or more screening holes are filled with a solid substance so as
to prevent the solid substance from becoming lodged within the
holes. The use of solid and inflexible rods or bars as reinforcing
members does not permit such flexing and removal of the filling
substance from the screening holes. Furthermore, the flexible
reinforcing members 15 of the rubber screen of this invention, may
allow certain parasitic oscillation of the rubber screen in
response to sieving vibration, which oscillation acts to prevent
the screen elements from being clogged. On the other hand, solid
and inflexible rubber bars or rods may not allow the rubber screen
to make such parasitic oscillation so that the screen holes are
more easily clogged. Still another advantage of the flexible
reinforcing members 15 of the present invention is that the rubber
screen can be rolled so as to facilitate its transportation and
insulation.
With the present invention, it is also possible to apply suitable
abrasion resisting rubber layers on the front and back surfaces of
the rubber screen, such as hard rubber layers and urethane rubber
layers, for the purpose of improving the durability.
As described in the foregoing, according to the present invention,
the performance characteristics of the rubber screen is
considerably improved, together with its durability. Furthermore,
the man-hours necessary for the replacement of the rubber screen in
a vibration sieve is greatly saved, in the case of any breakage in
the rubber screen. Thus, the present invention provides a
remarkable contribution to the industry.
* * * * *