IL123366A - Vibratory separator - Google Patents

Description

VIBRATORY SEPARATOR VIBTEC ENGINEERING LTD o"sn noun pom FIELD OF THE INVENTION The present invention relates to vibratory equipment, generally, and more particularly to vibratory screen separators for particulate solids materials, and for fine powder materials and especially to powder materials having a tendency to agglomerate.

BACKGROUND OF THE INVENTION The use of vibratory screen separators for the purpose of screening ultra-fine materials, such as powders, is well known. In general, powders are screened so as to remove therefrom large particles which, while having a presence of typically less than 10 % have a typical size in the range 20 -100 microns and their presence thus degrades the quality of the powder.

Screens used for fine and ultra-fine powders, which have a particle size of less than 3 microns, get blocked due to agglomeration of these powders. An agglomerated particle may accumulate to a size of 100-200 microns. This phenomenon gives rise to the blockage of screens, and prevents the use of screens of a smaller size, such as 100 microns, thereby effectively preventing many of above-described large particles, having a size of 20-100 microns, from being properly removed. In turn, this prevents the resultant materials from having greater than a desired purity. The main reason for the above-described agglomeration and blockage is a high cohesion both between individual particles and between the powders and screen mesh.

There are known in the art vibratory sieve separators, excited by centrifugal vibratory motors, for example tumbler screen separators, equipped by cleaning means for preventing screen blinding by particulate materials and powders. Typically these cleaning means are formed as anti-blinding insertion assemblies using bouncing balls, hollow rings, wiper blades or brushes, air-jet flow, ultrasonic and so on. Nevertheless, in screen processing of a number of fine powder materials, inclined to agglomeration of particles, these cleaning means are inefficient, having to stop a separator for periodical cleaning.

There is known a vibratory separator for separation of fine materials, powders and slurries, which is described in the book "Polymer sifting surfaces of vibratory screens", authors Nadutij, V.P. and Zolotareva V.L., publishing house NEDRA, Moscow, 1993, in Russian (see pp.42 and Fig. 3d). This vibratory separator comprises a vibrating housing, springs, a vibratory exciter, a screen and a supporting elastic net, spaced under the screen. The net is formed by a plurality of parallel stretched elastic strips strings, each of them has a set of teeth, so as a number of openings in the supporting net are formed. The size of the screen openings is equal to the separation boundary dimension. The size of supporting net opemngs exceeds the size of the screen openings of about 5 -10 times. Vibration exciter induces vibration of the screen and net strings. The latter are stretched in such a way, that the tuned strings and screen, been activated, interact in impact manner, and the screen under repeated impacts is cleaned from the particles of screened material, which stuck and clogged in the openings of the screen. The essential disadvantage of described screening is deficient throughout because the strings block a significant part of the screen openings from bellow, thus resisting to the passage of the solids particles through the screen. The residual open part of the screen is cleaned only due to impact acceleration on the neighboring screen parts, which are blocked.

Another shortcoming is the absence of cleaning efficiency on the side boundaries of the screen, where acceleration of the strings is too small for proper separation, thus the screen efficient open area decreases. The third disadvantage is the relaxation of the strings in time, which provokes changing the strings natural frequency, and therefore failure of the tuned vibration regime and cut of the screen capacity and reliability. The forth disadvantage is insufficient acceleration of the sieve surface, caused by low elastic energy of the strings.

In our Israeli application No. 120893 entitled 'Improved Vibratory Separator' the first, second and third disadvantageous of the previous screen separator were eliminated by means of using of de-agglomeration system rigid actuator, connected to the separator housing by special resilient mountings. However, acceleration level remains insufficient for proper self-cleaning of the sieve and de-agglomeration of 'difficult-to-screen' fine and ultra-fine powders. Besides, proposed deagglomeration system may to reduce quality of the screening processing because contact interaction of the elements with the top surfaces of the sieve element.

SUMMARY OF THE INVENTION It is thus an aim of the present invention to provide a vibratory screen separator for fine and ultra-fine powder materials which is characterized by continuous self-cleaning and also by disintegration of agglomerates of particles during use.

It is another object of the invention to increase the capacity and output of the undersized product for fine powders which have a tendency to form agglomerates of particles.

These two aims are achieved by transfening to the sieve element of high level acceleration, which is generated by activating means, comprising impact actuators and especially designed resilient mountings.

There is thus provided, in accordance with a preferred embodiment of the present invention, an improved vibratory separator for the screening of fine particulate material which includes a rigid housing, having a top cover portion and a bottom portion, the housing having an inlet for permitting the ingress of material to be screened into the interior of the housing, a first outlet for the exhausting of the undersized material, and a second outlet for the exhausting of oversized particles; vibratory motor mounted in excitation association with the housing; resilient support apparatus for the housing permitting excitation of the housing in response to operation of the vibratory motor, and a screen assembly.

The screen assembly includes a generally planar screen element, having upper and lower, generally parallel surfaces, disposed in said housing between said first outlet, and said inlet and said second outlet, such that material entering said housing through said inlet engages said screen element, and wherein undersized material passing through said screen assembly exits said housing through said first outlet, and wherein oversized material not passing through said screen exits said housing through said second outlet.

Also, vibratory separator includes at least one activating means located in association with said lower surface of said screen assembly, for cleaning said screen assembly and for disintegration of agglomerates of particles of material to be screened, and wherein said activating means is operative in response to operation of said vibratory means, and said activating means comprises: at least one rigid actuator, and at least two resilient mounting means for mounting said rigid actuator between said screen assembly and said first outlet, and operative to undergo, in response to excitation of said housing, a predetermined excitation different to that of said housing, and nirther operative to cause a corresponding excitation of said screen assembly.

Also, the rigid actuators are arranged in spaced relation with said lower surface of said screen assembly, and said resilient mounting means is operative to permit oscillation of said rigid actuators in response to excitation of said housing, and the amplitude of oscillation of said rigid members is greater than the spacing between said rigid actuators and said screen elements, such that all said rigid actuators are operative to impact said screen assembly during said excitation.

Also, said resilient mounting means comprises at least two elastic chains which chain comprises at least two elastic bushes, and said elastic chain have a first end and a second end, and the first end of said elastic chain is connected to said housing at least indirectly, and the second end of said elastic chain is connected to the said rigid actuator, at least indirectly.

Additionally in accordance with a preferred embodiment of the invention the elastic chains of the resilient mounts comprises elastic bushes having parallel axes.

Additionally in accordance with a preferred embodiment of the invention outer sleeves of said elastic bushes with parallel axes are attached to said housing and to said rigid actuator at least indirectly, and inner sleeves of said elastic bushes are connected together.

Additionally in accordance with a preferred embodiment of the invention the outer sleeves of said elastic bushes are fixedly connected each to other, and said inner sleeves are attached to said housing and said rigid actuator, at least indirectly.

Additionally in accordance with a preferred embodiment of the invention two elastic bushes of the resilient mounting means are placed in a single rigid body, and said inner sleeves are attached to said housing and to said rigid actuator, at least indirectiy.

Additionally in accordance with a preferred embodiment of the invention the resilient mounting means contains at least two pairs of elastic bushes with normally crossed axes.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawing, in which: Fig. 1 is a side view of a self-cleaning vibratory separator constructed and operative in accordance with a preferred embodiment of the present invention; Fig. 2 is a plan view of the separator of Fig. 1; Fig. 3 is a cross-sectional view of the separator of Figs. 1 and 2 taken along lines 3 - 3 therein; Fig. 4A-C are schematic side views of activating apparatus, employing a combination of elastomer bushes as resilient member of activating apparatus and formed in accordance with alternative embodiments of the inventions; Fig.5 is a schematic side view of the activating apparatus, employing a combination of pair elastomer bushes, having normally crossed axes.

Fig. 6 is the top view on the activating assembly in a further embodiment of the tumbler vibratory separator wim axialiy lined vibrator motor; Fig. 7A is an enlarged partial cross-sectional side view of the screen assembly and activating apparatus of the vibratory separator of Fig. 6, taken along lines 7 A-7 A therein; Fig. 7B is a plan view on the activating apparatus of the vibratory separator of Figs. 6 and 7 A, taken along lines 7B-7B; Fig. 8 is the top view on the activating assembly in a further alternative embodiment of the circular vibratory separator with outer disposition of the vibrator motor; Fig. 9 is a schematic cross-sectional side view of the screen assembly and activating apparatus of the vibratory separator of Fig. 8.

DETAILED DESCRIPTION OF THE INVENTION Referring now to Fig. 1-3, there is shown a vibratory separator, referenced generally 10, constructed and operative in accordance with a preferred embodiment of the present invention. The present invention is intended primarily for screening of powder materials having a tendency to agglomerate, and which typically have a particle size in the range 0.1 - 150 microns.

The separator 10 includes housing 12 having a cover 14, a screen assembly 18 supported in housing 12, and a vibratory motor or exciter 20, mounted onto cover 14 and housing 12. Motor 20 is typically any suitable vibratory motor having an operating speed in the range 750 - 3000 rpm. Housing 12 has attached thereto a plurality of flange supports 15, via which it is mounted onto any suitable support surface (not shown) via resilient supports 16, such as suitable springs, thereby to permit a suitable excitation to be set up in the separator 10 and to provide a suitable vibration insulation of the support surface. It will be appreciated that, as alternative to the illustrated spring mounting, housing 12 may be suspended from an appropriate support via elastic suspension elements. An inlet 22 for feeding material to be screened, is provided in cover 14, a first outlet 24, located beneath screen assembly 18, is provided for exhausting undersized material passing therethrough, and a second outlet 26 is provided, typically spaced longitudinally away from inlet 22, for discharging oversize material from separator 10.

Screen assembly 18 includes a screen element 28 of a predetermined appropriate mesh size, typically in the range 600 - 50 mesh having openings in the range 20 - 300 microns. Screen element 28 is supported by means of a screen support element 29, which is typically planar. Support element 29 is mounted onto housing 12 via a peripheral sealing 30 and a rigid support flange 32. The flange 32 is attached to the housing 12, as by welding. Support element 29, having suitable bending stiffness, typically is formed as single layer or several layers, each of them includes appropriate stiff punched metal or wire woven sieve. Openings or perforations of the screen support element 29 have essentially greater dimensions than ones formed in screen element 28. The respective dimensions of the support element 29, peripheral sealing 30, flanges 32, also mass and bending stiffness of the support element 29 are predetermined so as to retain screen 28 without essential tension, thus prolonging lifetime of the fine screen element 28. Typically, screen element 28 is formed of a suitable wire mesh of stainless g steel, brass, and so on or may be formed of a suitable polymers, nylon, and so on.

So as to prevent material to be screened from bypassing the 'active' area of the screen, there are provided a resilient sealing elements 42, each of which is confined in a rigid seating 44 extending downward from cover 14, and between cover 14 and peripheral sealing 30.

It will be appreciated that, as the material to be screened enters into housing 12 through inlet 22, which is located above screen 28, at least one activating apparatus, referenced generally 48, is located beneath screen assembly 18. The activating apparatuses 48 are formed of rigid actuators 52, which are spaced transversely to along the screen 29 parallel thereto and in spaced relation therewith. The quantity of activating apparatuses 48, shape and dimensions of actuators 52 are preferably such that actuators 52 extends along substantially the entire area of the screen assembly 18. While the actuators 52 are themselves rigid, they are supported on resilient mounts, referenced 54 so as to enable the development of a predetermined oscillation motion when motor 20 is operated. The resilient mounts 54 are typically the chain elastic links, which consist of suitable elastomer bushes, referenced 58. Each of chains is connected to the actuator 52 via a connecting portion 56, and to the housing 12 via a outer sleeves 53, end portion 38 and support flange 32. Inner sleeves 55 of the pair of elastic bushes 58 are connected together by a connecting fork 57, having the parallel rigid axes, inserted inside the inner sleeves 55 and locked by a strip lock member 59.

When the vibratory motor 20 is operated, activating apparatus 48 is excited by translating motion of the housing 12, and actuators 52 on resilient mounts 54 oscillate relatively housing 12 and sieve assembly 18. Actuators 52 in predetermined points of their patterns collide the screen assembly 18 with substantial relative velocity. Transferring an essential part of the kinetic energy to the elements of screen assembly 18, actuators 52 provide self-cleaning of screen assembly 18 and simultaneous de-agglomeration of the material to be screened by the way of vibratory pulverizing. It will be appreciated that as activating apparatus 48 of the present embodiment oscillates with significant amplitudes and velocities and actuators have significant masses, therefore high level impact acceleration, transferred to screen assembly 18 is sufficient for self-cleaning of the openings in the components of the screen assembly 18 and for disintegration of agglomerates of the material to be screened.

It will be appreciated that the bending stiffness of the screen support element is sufficient for transferring predetermined impact acceleration to all area of the screen 28, thus preventing clogging and blinding of the openings and providing disintegration of particle agglomerates. These advantages of the present invention are resulted by employing of elastomer bushes 58 in resilient mounts 54, admitted accumulation high deformation energy in limited dimensions.

Among advantages that were found in the present construction, are the following: 1. Self-cleaning and agglomeration prevention are performed continuously during operation of the separator, thereby enabling continuous use, without having to stop for periodic cleaning. 2. The proposed support of the screen assembly provides free mounting of fine screen 28 without any substantial tension, thus reducing wear and fatigue of the fine screen and increasing its life prior to replacement. 3. The cleaning and anti-agglomeration characteristics of the separator of the present invention have been found not to be adversely affected by an increase in the supply loading thereto of material to be screened. This is due to the fact that the actuators 52 have substantial kinetic energy.

In accordance with preferred embodiment of the invention, activating apparatuses 48 are spaced across to the typical path of the material to be screened from inlet 22 to outlet 26. In accordance with an alternative embodiment of the invention activating apparatuses 48 may be spaced also along the typical path of the material or acute-angled to this direction.

Also, actuator 52 may be covered by an appropriate lining, attached to the surface of actuator 52, which is contacted with the screen assembly 18. The lining may be made from wear-proof material such as polyurethane, rubber and so on.

It will be appreciated by persons skilled in the art that, in accordance with an alternative embodiment of the invention, the actuators 52 may form part of or be replaced by a rigid network or coarse screen. In the alternative case the actuators may be equipped in their top part by the elastic bars or by the rigid bars, fastened resiliently to rigid actuators.

Also, the surface of the support screen 29 from the side, which is contacted with actuator 52, or part of this surface may be covered by an appropriate lining made from wear-proof material.

For screening of several materials it is preferable may be embodiment of the present invention where screen assembly 18 contains supporting screen 29, which is tensioned similar to construction of conventional screen. Fine screen 28 of the screen assembly may be mounted without any tension or with gentle tension. Such a low-force tension is significantly less than u one in the conventional fine mesh powder screens. In the latter case screen assembly may be constructed without any support element.

Elastic bushes are known in the art and, for example, may be Silentblock elastic bushes sold by the US company Clevite Elastomers or UD UltraDuty type elastic bushes sold by the Great Britain company Metalastic Vibration Control Systems. Typically, an elastic bush is an axially symmetric elastomer-metal part, which consists of an annular rubber bush inserted coaxially between an inner metallic sleeve or rod and outer metallic sleeve.

Referring now to Fig. 4A there is shown a further alternative embodiment of the invention with elastomer bushes 58 having a fixed bracket portion 43 and thread portion 41 for fastening to housing 12 and to actuator 52. These portions may be attached to the outer sleeves 53 directly, as welding, for example. Alternatively, bracket portion 43 or thread portion 41 may be attached to elastomer bushes 53 indirectly, via intermediate hub (not shown), elastomer bushes 53 may be pressed up therein.

Referring now to Fig. 4B there is shown a further alternative embodiment of the invention with elastomer bushes 58 having outer sleeves 53 connected each to other by a predetermined axis-to-axis distance. Such a construction of resilient mounts 54 simplifies assembling and service of the activating apparatuses 48.

Referring now to Fig. 4C there is shown a further alternative embodiment of the resilient mount 54 with two elastic are placed in a single rigid body 59, and inner sleeves 55 are attached via bracket ends 43 to housing 12 and to rigid actuator 52, thus simplifying resilient mount and improving rehability.

Referring now to Fig. 5, there is shown a further alternative embodiment of the activating apparatus, generally 48, of the present invention. Actuator 52 is connected to the housing portion 12 by means of resilient mounts 54, each of them is formed as chain link of two pairs 59' and 59" of elastomer bushes, which are rigidly connected together. Elastomer bushes 58' and 58" assembled in the pair 59' and elastomer bushes 58"' and 58"" assembled in the pair 59" have mutually normal crossed axes 71 and 72. Inner sleeves 55 of elastomer bushes 58" are fastened to vibrating housing 12 via flanges 38. Inner sleeves of elastomer bush 58"' of the pairs 59 " are fastened to actuator 52. Inner sleeves of elastomer bushes 58' and 58"", belonging to different pairs 59' and 59", connected together by means of fork 57. Such a design of resilient mounts 54 provides essential two-dimensional dynamic boosting of oscillation of actuator 52, and thus velocity of material in transportation direction may be increased.

Such an embodiment of the present invention improves cleaning of the sieve elements in the case of the when only one fine screen mesh is used in the screen assembly.

Referring now to Figs. 6 - 7A,B there is shown the activating assembly of the vibratory tumbler separator, generally referenced 110, constructed in accordance with a further alternative embodiment of the invention. This part may form an insertion assembly, which combines a screen assembly, generally 118 and set of activating apparatuses 148, assembled in a joint circular housing unit, 112. Typically, the latter may be inserted to a tumbler separator.

The screen assembly 118 includes a screen element 128, screen support element 129 and a peripheral sealing 130 (not shown). These elements are similar to mat shown and described above in conjunction with Figs. 1-3 and is thus neither shown in details nor described again herein.

The activating apparatuses 148 are formed of rigid actuators 152, having a first connection portion 156' and a second connection portion 156" for rigid connection of the ends 143 of resilient mounts 154 thereto. Support element 138 fastens outer sleeves of elastomer bushes 158' to the housing portion 112 via rigid support flange 138. The actuators 152 are typically spaced in parallel to the screen assembly 118, thus providing impact processing of the elements of the screen. The operation of the activating apparatuses 148 is generally as described above in conjunction with Figs. 1-3 and is thus not described specifically herein.

Referring now to Figs. 8-9, there is shown a further alternative embodiment of the activating assembly of the vibratory separator, where are employed activating apparatuses, generally referenced 248, for the tumbler screen separator, in which the sieve assembly oscillates in the plane thereof. The activating assembly, generally 264, includes two activating apparatuses, 248'and 248". The latter have actuators referenced 252' and 252", which rigidly connected together each to other by means of essentially rigid frame, generally 263, which includes portions 26 Γ, 262 and 261". When vibratory motor 220 is operated, the frame 263 rotationally oscillates relatively to housing 212, under translation motion of the vibrating housing 212, thus forcing the activators 252' and 252" to impact in turns the support sieve element 229 of the screen assembly 218. It will be appreciated that the predetermined eccentricity of the frame 263 generates alternative vibration moment, thus providing to actuators 252' and 252" significant kinetic energy, which further is transferred to sieve assembly 218. 123366/2 Referring now to Figs. 10A-10C, there is shown the activating assembly of a tumbler vibratory separator, generally referenced 310, constructed in accordance with a further alternative embodiment of the invention. This part may form an insertion assembly, which combines a screen assembly, generally 318, and one or more activating apparatuses, referenced generally 348, assembled in a single circular ring 312. Typically, the ring 312 may be inserted in the housing of the tumbler separator screen which vibrates parallel to the screen assembly 318.

The screen assembly 318 includes a screen element 328, screen support element 329 and a peripheral sealing 330 (not shown). These elements are similar to that shown and described above in conjunction with Figs. 1-3 and are thus neither shown in detail nor described again herein.

The activating apparatus 348 is formed of rigid actuator 352, having two connection portions 356 for rigid connection of the ends 343 of resilient mounts 354 thereto via U-bolts 329'. Support element 338 fastens outer sleeves of elastomer bushes 358 to the housing portion 312 via rigid support 332 and U-bolts 339. This connection is provided so as to render inclination of the axes of elastomer bushes 358 adjustable. The angle of inclination a of the bushes 358 is in the range 0 - 90°. The respective axes of bushes 358, 358', 358" and 358'" are thus also inclined accordingly, by angle a, with respect to sieve element 328. Accordingly, excitation of housing and support element 332 which, as described above, is parallel to sieve element 328, is transformed into an inclined vibratory motion of the actuator 352 which is inclined relative to the sieve assembly 318.

It will be appreciated that the particular construction shown and described above in conjunction with Figs. 10A-10C, is by way of example only, and that the present invention includes any construction which enables screening in accordance with the method of the invention, and wherein the vibration of the screen assembly is parallel to the screen element.

It will further be appreciated by persons skilled in the art that the scope of the present invention is not limited to what has been shown and described hereinabove, merely by way of example. Rather, the scope of the present invention is defined solely by the claims, which follow.

Claims (9)

1. A vibratory separator for screening of fine powder materials which comprises: a rigid housing, having a top cover portion and a bottom portion, said housing having an inlet for permitting the ingress of material to be screened into the interior of said housing, a first outlet for the discharge of undersized material, and a second outlet for the discharge of oversized particles; vibratory means mounted in excitation association with said housing; resilient support means for said housing, permitting excitation of said housing in response to operation of said vibration means; a screen assembly which includes a generally planar screen element, having upper and lower, generally parallel surfaces, disposed in said housing between said first outlet, and said inlet and said second outlet, such that material entering said housing through said inlet engages said screen element, and wherein undersized material passing through said screen assembly exits said housing through said first outlet, and wherein oversized material not passing through said screen exits said housing through said second outlet; at least one activating means located in association with said lower surface of said screen assembly, for cleaning said screen assembly and for disintegration of agglomerates of particles of material to be screened, and wherein said activating means is operative in response to operation of said vibratory means, and said activating means comprises: at least one rigid actuator, at least two resilient mounting means for mounting said rigid actuator between said screen assembly and said first outlet, and operative to undergo, 123366 / 2 in response to excitation of said housing, a predetermined excitation different to that of said housing, and further operative to cause a corresponding excitation of said screen assembly, and said rigid actuators are arranged in spaced relation with said lower surface of said screen assembly, and said resilient mounting means is operative to permit oscillation of said rigid actuators in response to excitation of said housing, and the amplitude of oscillation of said rigid members is greater than the spacing between said rigid actuators and said screen elements, such that all said rigid actuators are operative to impact said screen assembly during said excitation, and said resilient mounting means comprises at least two elastic chains which chain comprises at least two elastic bushes, and said elastic chain have a first end and a second end, and the first end of said elastic chain is connected to said housing, at least indirectly, and the second end of said elastic chain is connected to the said rigid actuator, at least indirectly.

2. A vibratory separator according to claim 1, wherein said elastic chains comprises elastic bushes having parallel axes.

3. A vibratory separator according to claims 1 or 2, wherein outer sleeves of said elastic bushes are attached to said housing and to said rigid actuator at least indirectly, and inner sleeves of said elastic bushes are connected together.

4. A vibratory separator according to claims 1 or 2, wherein outer sleeves of said elastic bushes are fixedly connected each to other, and said inner sleeves are attached to said housing and said rigid actuator, at least indirectly. 123366/3

5. A vibratory separator according to claims 1 or 2, wherein said two elastic bushes of said resilient mounting means are placed in a single rigid body, and said inner sleeves are attached to said housing and to said rigid actuator, at least indirectly.

6. A vibratory separator, according to claim 1, wherein said elastic chains comprise at least two pairs of elastic bushes with normally crossed axes.

7. A vibratory separator according to claims 1-5, wherein axes of said elastic bushes are inclined by an angle a in the range 0-90° relative to the plane of the sieve assembly.

8. A vibratory separator according to any of claims 1-7, and substantially as shown and described above in conjunction with any of Figs. 1-l OC.

9. A vibratory separator according to any of claims 1-7, and substantially as shown in any of Figs. 1-lOC. For the Applicant, Jeremy M. Ben-David & Co. Ltd. VIB 210/3.1