AU423552B2 - A rubber screen for a vibrating sieve - Google Patents

Description

14,,99 0170 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 nay 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, its rusts, and the clogging of the mesh. 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 suLch difficulties of known metallic wire screens and rubber screans, 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 accompa..,'Ing draw-ngs, in which: Fig. I.is a perspective viet... of a knovm vibrating sieve using a metallic wire screen;

423.552

14990/70 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 mount-

ing 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 joint portions of a rubber screen according to

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14,99070 -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 Fir.. 3, are bent along the lower edge of each clamping bar 4i, 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 nutp 6. A holding- bar 11 is disp osed 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 hol d 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,, frmed on the side plates 9, for preventing the clamping barc.-1 from slipping along the side plates during the vibration. EZ.ch side plate 9

42 3.55 2

14.990/70 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. rusts 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 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

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

5 42 3.55 2 apetues 3.14.990/70 through the aprue 3.Thus, the finer parti~cles or the substance thus fed are separated from coarser particles. The known rubber screen, however, has the following draft-backs. During the sifting operation, the rubber screen 12 Itself vibrates while forming nodes at the clamping bars Ii and a holding bar 11. Such vibration of the rubber screen 12' is shown by two-dot-dash lines in Fig. 4i. The amplitude of such vibration of the rubber screen can become very large under certain condition~s. If a light substance with a comparatively small specific gravity, 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 114 are secured to longitudinal fram .emembers 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. II. The additional holding bars 141, 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 14I Is not preferable. If no extra holding bars 121 ar~e added, the pulverized or granulated substance flowing on' the rubber

6 42 3552

14,99 0/70 screen tends to concentrate in spaces between adjacent

longitdudinal frame members 3, inclusive of the central

member If the substance being sifted has a compara- tively 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 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.

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

7- 423.552

14.990170 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

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.

In the embodiment of Fig. 6a, the reinforcing members

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

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

is possible relative to the flow direction A, for

instancesat 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 of each reinforcing

member 15 extend sideway from the side edges of the

sifting portion of the rubber screen 12, to form ribs

r and The ribs r, r' thus extended can be bent along

the lower edges of the clamping bars 4, as described herein-

before referring to the metallic wire screen 1 of Fig. 1.

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14.990/70 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 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 Fig. 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 members 15 in the rubber screen

12 by means of the ribs r and 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.

-9- 4.2 3.552

14. 9 9070 Figs. 7e and 7f illustrate another embodiment of the termination of reinforcing members 15. The end Portion 16 of each reinforcing member 15. is turned back so as to form a foided 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 reinforcing 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 assemb ly 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 sboiqn In Fig. 7e, the stopper plate 15a is Integrally secured to the reinforcing member 15. Thus, the stopper plate 15a hold the reinforcing member

against a tension tending to pull the reinforcing member 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 In the form of a strap. With the construction of the ribs r and as shown in any one of Figs-. 7a to 7f, the reinforcing members buried In the rubber screen 12 can be tightly secured to the side plates 9, by means of the clamping bars 14and the fastening means consisting of bolts 5 and nuts 6. If the length of each re~nforcing member 15 is suitably

10 42 3.5~52

14. 99 0/70 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.

33

423.552

14 99 0170 The rubber screen .12 made of such compound

rubber materi1a 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 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 embedding

in the intermediate portions of the rubber screen 12 with-

out compound rubber, as described hereinbefore referring

423.552 to Figs. 6a to 6c. 4907 Accordingly, with the'rubber screen of the present invention, there will be no vibration of large hold- amplitude in the rubber screen between the central ing bar and the side plates. The risk of the dropping of the particles, which are being sifted, over the side plates is completely eliminated. Besides, the number rubber of the holding bars 11 necessary for holding the be screen of the present invention on the sieve can minimized. Furthermore, when it is desired to form a long rubber screen by connecting a plurality of unit screens, the rubber screen of the present invention are particularly advantageous. Referring to Figs. 9a and 9b, at the 12, connecting portion b of adjacent rubber screen units the edges e, e'of the abutting rubber screens 12 include reinforcing members 15 embedded therein, respectively. The-abutting edges are slantly cut, as test 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, bur:ps at the connecting portions of the adjacent rubber screen units, which havre been experienced In conventilonal rubber screen as shown in Figs. 5a and can completely be eliminated. Consequently, smooth flow of pulverized or granulated substance being sifted is ensured, an~d the sifting efficiency is considerably improved. The el~mination of the bumps at the connecting

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1 4.99 0170 in portions of the adjacent rubber screen units results rubber screen the complete removal of the striking of the of the wear by the substance being sifted, and the degree of the rubber and tear is reduced, so that the service life screen Is also greatly improved. In mounting the rubber screen 12 of the inven-

tion, it Is preferable to stretch it in a direction being lateral to the flow direction A of the material the reinforc- sifted, so as to apply a suitable tension to rubber. Ing members 15 or short fibers in the compound of Sucb tension acts to reduce the vertical vibration the the reinforcing members, or the. short fibers, at longitudinal frame nenbers. 3 and and accordingly the rubber tension suppresses tte vertical vibration of the 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 which was screen In the proximity of such frame members, also experienced with conventional rubber screens, is substantially eliminated. Thus, the wearing of the

rubber screen becomes uniform over the entire span thereof. Such elimination of the local wear also con- of the -tributes- to the improvement of the service life rubber scren. Wdith the present invention, it Is also possible on the to apply suitable abrasion resisting rubber layers as front and back surfaces of the rubber screen', such for the hard rubber layers and urethane rubber layers, purpose of improving the durability. -As described In the foregoin'g, according to the

14 4238.55 114 2

4 99 0 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.

15 423.552

Claims (1)

1 9 9 0/70 THE CLAIMS DEFINING THE INVENTION AR 'AS FOLLOWS:

1. A rubber screen for the use in a vibration

sieve for separating smaller particles of a substance

being sifted from larger particles thereof, comprising

a planar body.made of rubber-like resilient material,

and a plurality of apertures bored therethrough for

passing the smaller particles, characterized in that at

least two inextensible reinforcing members made of

steel ropes, steel wires, and/or fibrous cords are

embedded in the screen so as to extend across the

entire width of said planar body at right angles to the

flow direction of the substance being sifted, and

mounting means integrally formed by uprightly bending

opposite edges of the planar body which are parallel

to the flow direction of the substance being sifted,

said mounting means being reinforced by bending

opposite ends of the reinforcing members and embedding

the opposite ends of the reinforcing members in the

opposite edges of the planar body, said rubber screen

being mounted on the vibrating sieve by securing the

mounting means to the sieve, while providing a high

lateral rigidity to the rubber screen relative to the

flow direction, whereby the screen i.s kept tautly

spread while being prevented from localized vibration

relative to remainder of the screen or the plane of

the screen.

2. A rubber screen according to claim 1,

characterized in that the screen further comprises a

pair of grooves formed on the upper surface thereof in

parallel with the flow direction of the material along

the edges thereof, so as to constitute said mounting

means. 16 423.552

14 9 0 70 3. A rubber screen according to claim 1,

characterized in that said mounting means further

consists of stopper plates with small apertures and

stopper pins, each end portion of the continuous

reinforcing member being so bent as to form a folded

end portion, each stopper plate being coupled to the

end portion of the reinforcing member by inserting

the folded end portion thereof through the aperture

of the end plate from one side of the plate so as

to slightly project the folded tip of the reinforcing

member out of the opposite side of the plate, each

stopper pin being forced into a closed loop defined

by the folded tip of the reinforcing member projecting

from said opposite side of the stopper plate and the

stopper plate per se, the stopper plates thus coupled

to the end portions of the reinforcing members being

embedded in the rubber screen along opposite edges of

the rubber screen.

4. A Rubber Screen for a Vibrating Sieve

according to claim 1 substantially as hereinbefone

described with reference to the accompanying drawings.

DATED this 19th day of JANUARY, 1972. BRIDGESTONE TIRE COMPANY LIMITED By its Patent Attorneys: CLEMENT HACK CO. Fellows Institute of Patent Attorneys of Australia.

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423.552