Patent Grant
7735656
This invention directs itself to rotary screening systems for separating particulates by size. In particular, this invention directs itself to a self-clearing rotary screening system that prevents the formation of excessive clogging of the screening apparatus. Still further, this invention directs itself to a rotary screening system that includes a system of displaceable members, wherein each of a plurality of displaceable members are pivotally displaced responsive to rotation of a rotary framework of the rotary screening system. During rotation of the rotary framework, the displaceable members in the form of displaceable screening members are subjected to rapid deceleration that breaks loose agglomerations of material that are caked onto the screen. Additionally, the rapid deceleration of the displaceable screening members can be accompanied by impacts of one screening member striking another. More in particular, this invention pertains to a method of retrofitting a rotary screening apparatus which includes the steps of providing a plurality of longitudinally extending screening members, locating the screening members internal to a longitudinally extended material receiving cavity of the rotary screening apparatus in angularly spaced relationship, and pivotably mounting the plurality of screening members a distance one from another so that each of the screening members strikes an adjacent other of the screening members during rotation of the rotary screening apparatus. Still more in particular, this invention is directed to the inclusion of displaceable members in the form of flexible belts overlaying imperforate portions of the rotary screening apparatus. Agglomerations of material that have bound themselves to the flexible belts are loosened due to the gravitational effects on the belts during rotation of the rotary screening apparatus causes, thereby keeping the imperforate portions of the rotary screening apparatus clear. Yet further, this invention directs itself to a rotary screening system that includes a system of displaceable members in the form of a plurality of displaceable mallets. The plurality of mallets are arranged in sets that are angularly spaced one from another. Each set of mallets include a multiplicity of longitudinally spaced mallets that impact against the screens of the rotary screening apparatus responsive to the rotation thereof. Additionally the mallets of each set are different lengths to strike screens of rotary screening apparatus in different areas.
Rotary screening systems are well known in the art. One of the most common prior art rotary screening apparatuses is known as a trommel screening device, and is generally cylindrical in shape, open at both ends, and when in use is rotated to sort material by size. The cylindrical trommel screening device is inclined with the material to be processed dumped in the higher end. Rotation of the screen causes the material to tumble towards the lower end. The material, which is smaller than the openings in the screens that define the periphery of the cylinder, fall through those openings to be carried off by conveyors, or otherwise collected for further processing, while the coarser fraction of the material is discharged out the lower end.
Often, the material to be screened is exposed to the environment for considerable periods of time before being processed, and thereby accumulates moisture. While some of the material processed by trommel screens is inherently moist. Those conditions lead to a major problem that occurs when operating these screening devices, that of excessive clogging of the screening material, often referred to as “blinding the screens”. The moist material being screen tends to agglomerate and become and become bound or “caked” on the screens. The screening “drums” often have annular imperforate bands by which the rotary screening drum is rotatively supported. These solid portions of the rotary frame also become caked with the agglomerations (“mud”) that binds itself thereto. The bound agglomerations impede the longitudinal flow of the material through the drum, thereby detrimentally effecting the efficiency of the screening operation. Excessive clogging of the screens and/or the caking of material on the imperforate portions of the drum requires an increase in the number of operators for the equipment, in order to tend to clearing out of the bound agglomerated material. Further, excessive downtime is required for performing the clearing operations to remove the bound agglomerations. Both the increased labor and increased downtime further reduce the efficiency of the apparatus and screening process.
The prior art has attempted to overcome this problem in a number of different ways. Many systems incorporate heaters to promote drying of the material being screened as it tumbles through the cavity of the trommel screening apparatus. Other systems have attempted to overcome this problem by forming the screens from a set of longitudinal bars that are wrapped by a set of circumferential rings, some of the longitudinal bars being movably mounted to the drum so as to be shifted in place in order to release the clogged material. However, none of these methods have satisfactorily alleviated this problem. The present invention by virtue of its self-clearing screening system automatically breaks up and unclogs agglomerated material from the screens which perform the primary screening function during each rotation of the rotary screening apparatus. The self-clearing screening system prescreens the material screened by the screens that define the periphery of the rotary screening apparatus.
The present invention is directed to a self-clearing rotary screening system. The system includes a frame having longitudinally extending axis. The frame includes a plurality of longitudinally extending frame members disposed in angularly spaced relationship, one with respect to another, about the axis. The system includes a plurality of first screening members affixed between respective pairs of the plurality of frame members to define a longitudinally extended cavity. A drive system is included in the rotary screening system and is coupled to the frame for rotating the frame about the axis. Still further, the system includes a plurality of second screening members hingedly coupled to respective ones of the plurality of frame members. The second screening members are pivotably displaced responsive to rotation of the frame about the axis.
From another aspect, the present invention is directed to a self-clearing screening system for application to a rotary screening apparatus having a plurality of longitudinally extending frame members disposed in angularly spaced relationship about a rotational axis thereof and a plurality of fixed screening members extending between respective pairs of the plurality of frame members for rotation therewith. The plurality of fixed screens define a longitudinally extended cavity into which material to be screened is delivered. The system includes a plurality of displaceable screening members disposed within the cavity. Each of the displaceable screening members is pivotably coupled to a respective one of the plurality of frame members. The displaceable screening members are pivotably displaced responsive to rotation of the frame about the axis. By that arrangement, the material to be screened is first screened by the displaceable screening members prior to being screened by the fixed screening members.
From still another aspect, the present invention is directed to a method of retrofitting a rotary screening apparatus with self-clearing screens. The method includes the step of providing a plurality of longitudinally extending screening members and locating at least a portion of the plurality of screening members internal to a longitudinally extended material receiving cavity of the rotary screening apparatus in angularly spaced relationship with respect to a rotational axis of the rotary screening apparatus. The method also includes the step of pivotably mounting the at least a portion of the plurality of screening members a distance one from another so that each of the at least a portion of the screening members strikes an adjacent other of the at least a portion of the plurality of screening members during rotation of the rotary screening apparatus.
From yet another aspect, the present invention is directed to a self-clearing screening system for application to a rotary screening apparatus having a rotary frame adapted for rotation about a rotational axis thereof. The rotary screening apparatus includes a plurality of screens mounted to the rotary frame for rotation therewith. The plurality of screens define a longitudinally extended cavity into which material to be screened is delivered. The self-clearing screening system includes a plurality of displaceable members disposed within the cavity. Each of the displaceable members has an end portion coupled to a respective portion of the rotary frame to be displaceable responsive to rotation of the rotary frame about the axis. By that arrangement, binding of the material to be screened and agglomerations thereof are cleared from portions of one of the rotary frame, or the screens, by the displaceable members.
a is a cut-away diagrammatic view showing the addition of a stop plate to the structure shown in
a is a cut-away diagrammatic view showing the addition of a stop plate to the structure shown in
Referring now to
Referring particularly to
The rotary screening apparatus 100 includes a base 102, which may be adapted for mobility as shown, or fixed in place. Base 102 supports a fixed framework 104 and a rotary frame 110, to which a plurality of fixed screening members 116 are secured. The rotary frame 110 has a longitudinal axis 112 about which it rotates, carrying the fixed screening members 116 therewith. Screening members 116 form an outer peripheral wall of the rotating frame 110 and define a longitudinally extended cavity 118 into which the material 50 to be separated is fed.
Particulate material 50 to be separated by the rotary screening apparatus 100 is fed into the cavity 118 through a hopper 126. The fines pass through the screening members 210, 116 as the rotary frame 110 is rotatively driven by a drive system 120 about the longitudinal axis 112. Drive system 120 is conventional and thus the details thereof are not described herein. Typically, the rotary frame 110 is disposed at an angle, with the material 50 being supplied to the higher end so that the rotation of the rotary frame 110, and screens 210, 116 therewith, causes the material to tumble towards the lower discharge end 108. The fines 50′ which pass through the screens 210, 116 are deposited on a conveyor beneath the rotary frame 110 (not shown) and carried to an outgoing conveyor 122 for transport away from the system 300, an arrangement which is well known in the art. The balance of the material 50, the material that is too coarse to pass through the screens, exits the apparatus 100 from the discharge end 108 to be carried away by other conveyors or material moving equipment.
Rotary frame 110 includes a plurality of longitudinal frame members 114, disposed in angularly spaced relationship with respect to the longitudinal axis 112. The plurality of longitudinally extended frame members 114 are joined to the ends of the rotary frame 110 and may have any number of intermediate orthogonally directed frame members extending therebetween, not important to the inventive concepts being disclosed herein. The fixed screening members 116 span between adjacent longitudinally extending frame members 114, and are angularly spaced one from another. Depending upon the longitudinal extent of the rotary frame 110, multiple fixed screening members 116 may be disposed longitudinally one adjacent another, as shown in
Referring now more particularly to
As further shown in
Extending transversely from one longitudinal side of the lower frame 218, are a plurality of pivot plates 222 disposed in longitudinally spaced relationship. The pivot plates 222 may be disposed in spaced pairs to define hinge knuckles which are pivotally coupled in the conventional manner to corresponding knuckles extending from the respective longitudinal frame members 114, or hinge plates (not shown) mounted thereto. As the hinge construction of the displaceable screening members 210 are well known in the art, such is not described in any further detail herein. The longitudinal dimension of the displaceable screening members 210 is determined by practical considerations relating to manufacturability, ease of assembly and the longitudinal dimensions of the rotary frame 110, as examples. Whereas, the lateral dimension A of each of the displaceable screening members 210 is established in order to facilitate the self-clearing function of the displaceable screening members. The dimension A is of sufficient dimension so that at a given position during rotation of the rotary frame 110 a displaceable screening member 210 will contact one other displaceable screening member 210 before striking yet another displaceable screening member 210.
Referring back to
As the rotary frame 110 rotates still further, the displaceable screening member in the position of displaceable screening member 210c, swings through an arc indicated by the directional arrow 20, to strike displaceable screening member in the position of displaceable screening member 210b, at that point in time, the screening member that was in position 210c overlaps the screening member which is in position 210b. Obviously, earlier in the rotational cycle, the displaceable screening member in position 210d had overlapped the screening member in position 210c when it was in the position of the screening member 210b. That overlap created in interference which had to be overcome by the effects of gravity on the screening member in the position of screening member 210c. Thus, the rotary frame 110 must rotate through a particular angular extent before the displaceable screening member in the position of screening member 210c drops down to strike the adjacent screening member 210b. That angular extent is greater than if there had not been the interference between the screens, thereby increasing the potential energy of the screen in the position of screening member 210c when it swings free to strike the screen in the position of the screening member 210b.
The interference between the two screening members in positions of the screening members 210c and 210d will have at least two beneficial effects. First, as the distal edge of the screening member in the position of screening member 210c slides along the surface of the screening member in the position 210d, it will scrape residual caked debris therefrom and cause vibration of the screening member in position 210d, which further aids in clearing material clogging the openings of the screen. Still further, the scraping by screening member 210c also creates a vibration in that screening member that aids in loosening clogged material thereon. Then, when the displaceable screening member 210c strikes the screening member 210b, such further unclogs the screening material thereof. During further rotation, as the displaceable screening member moves from the position of the position 210d to 210e, the displaceable screening member will have yet another impact that provides a further opportunity to “knock” free any caked on material.
That self-clearing process then repeats continually as the rotary frame 110 is rotated about the longitudinal axis 112 by the drive system 120. Although not important to the inventive concepts disclosed herein, the drive system 120 may include rollers 124 for support of the rotary frame 110 during rotation thereof. Rollers 124 may also be driven rollers to impart the rotational force to the rotary frame 110, for lighter duty applications. For heavy duty applications the rollers may be replaced by a gear drive system to positively drive the rotary frame 110.
In
Turning now to
Each displaceable screening member 210 is restrained by at least one flexible restraining member 232 coupled between the displaceable screening member and the rotary frame 110. The restraining member 232 may be in the form of a chain, cable or strap which acts to limit the pivotal displacement of the corresponding displaceable screening member. Thus, as the rotary frame 110 rotates about the longitudinal axis 112, the particulate material 50 either passes through the respective screen material 212 or tumbles from one displaceable screening member 210 to fall on a following displaceable screening member 210.
As a displaceable screening member 210 reaches a position somewhere between that of the screening members 210b and 210c, it begins to pivot about the hinged coupling 220, and being unrestrained by an adjacent displaceable screening member 210, is essentially in a freefall until it reaches the extent of the length of the restraining members 232 coupled thereto. The sudden deceleration of the screening member in the position of displaceable screening member 210c by the restraining members 232 provides an impact which frees caked on materials, which then by inertia are displaced into the cavity 118. The impact caused by restraining members 232 can result in recoil of the displaceable screening member 210 which is then followed by subsequent smaller impacts that that will induce a vibration in the screening material 212, to further aid in clearing clogging the screening material 212.
As in system 200, system 200′ may include a plurality of stop plates 230, as shown in
The number of displaceable screening members 210 in displaceable screening system 200, 200′ is a function of the perimeter dimension of the cavity 118 of the rotary screening apparatus 100, and may be a function of a number of longitudinal frame members and distance therebetween for retrofit applications. The number of displaceable screening members is not important to the inventive concepts, only that they define a screening surface area that essentially prescreens the particulate material 50 prior to the material passing through the fixed screening members 116. While the embodiment of
Self-clearing rotary screening system 300″ is shown in
As the rotary frame 110 continues to rotate, the displaceable screen in the position of displaceable screen 210c′ will be effected by gravity to swing down and strike the displaceable screen in the position of displaceable screen 210d′. The distal end 224 of the displaceable screen 210c′ will strike the adjacent screen 210d′ and due to the flexible nature of the screen and the swinging of the screen 210d′, bounce and scrape therealong until it is free of the displaceable screening member 210d′. That action induces vibration in both of the two interacting displaceable screening members. Once free of contact with the adjacent screening member, the screening member in the position of the displaceable screening member 210c′ will then strike the displaceable screening member in the position of displaceable screening member 210W, impacting thereon, recoiling and impacting again, causing vibrations within the screen 210b′ and itself. The vibration and impacts result in at least a portion of the otherwise clogging particulates to be displaced from each of the screening members. Further, any residual particulates imbedded in the screening member 210c′ will be removed when that screen is in the position of displaceable screen 210d′ and is struck and scraped by the screen is then positioned in the position of the screening member 210c′.
Particulates that remain embedded in the screen of the displaceable screening member 210b′, have two more opportunities to be jarred loose as the screening member is advanced into the positions of displaceable screening member 210c′ and 210d′. As the rotary frame continues to rotate, the displaceable screen that was in the position of screening member 210c′, becomes repositioned as it is brought into the positions of screening members 210e′ and 210f′. That cycle repeats for each of the displaceable screens as the rotary frame 110 is rotated about the longitudinal axis. In order to avoid any of the particulate material 50 from wedging between the distal end 224 of any of the displaceable screening members and a respective longitudinal frame member 114, each of the longitudinal frame members 114 are fitted with a stop plate 230, which supports the distal end 224 of an adjacent displaceable screening member 210a′-210f′, as in system 200 and 200′.
Turning now to
In order to stiffen the distal end 224 of the displaceable screening members 210′, a distal end portion 213 of the screening material 212 is wrapped around a core member 228. Core member 228 may be formed of steel wire, steel cable, a composite material being a tubular or solid rod structure, or another structure which provides stiffening and strength for enduring the repeated impacts to which each of the displaceable screening members are exposed. To further add strength and resiliency, the distal end portion 224 is encased with polymeric composition 226. Polymeric composition 226 may be a urethane material molded over the distal end, as well as materials such as epoxy, various thermoplastics and synthetic or natural rubber compositions. By that arrangement, the distal end 224 of the displaceable screening member 210′ acts as a mallet for imparting impact and vibrational forces on adjacent displaceable screening members 210′ during the rotative cycle of the rotary frame 110. Where further stiffness of the screening members 210′ is desired, the core member 228 of each screening member 210′ is extended in length and borders both longitudinal ends of the screening material 212. The screening material 212 at each longitudinal end is wrapped around the core member 228 in the same manner as the distal end portion 213. As an alternate to extending the length of core member 228, individual core members can be used at each of the longitudinal ends of each screening member 210′ with the screening material wrapped thereon.
As in the displaceable screening members 210, the longitudinal dimension of the displaceable screening members 210′ is determined by practical considerations relating to manufacturability, ease of assembly and the longitudinal dimensions of the rotary frame 110, as examples. Whereas, the lateral dimension A of each of the displaceable screening members 210′ is established in order to facilitate the self-clearing function of the displaceable screening members. The lateral dimension A is of sufficient dimension so that at a given position during rotation of the rotary frame 110 a displaceable screening member 210′ will contact one other displaceable screening member 210′ before impacting against yet another displaceable screening member 210′.
With reference to
The flexible belt members 310 may be formed of natural or synthetic rubber, various reinforced or unreinforced polymeric materials, leather and other flexible materials. Salvaged conveyor belts have been cut to size and also successfully used to form the belt members 310. Each of the belt members 310 is dimensioned to substantially overlay a portion of a corresponding annular rotary frame member 1102 disposed between a respective pair of angularly spaced longitudinal frame members 114. Multiple belt members 310, rather than one, may be angularly spaced in each arcuate sector of the rotary frame, between the respective pairs of angularly spaced longitudinal frame members 114, particularly where the screening apparatus is of large diameter. However, consideration must be given to the fact that belt members of greater length are subject to a greater amount of displacement activity and thereby tend to be more effective at breaking up the agglomerations of material bound thereto. The trailing end portion of each belt member 310, with respect to rotation of the rotary frame 110, is secured to the rotary frame 110. The belt members may be affixed to the corresponding annular rotary frame member 1102 itself by conventional fasteners 302, as shown in the drawing figures. Alternately, each of the belt members may be similarly fastened to a portion of a respective adjacent longitudinal frame member 114.
Referring in particular to
As the rotary frame 110 rotates still further, the belt member in the position of belt member 310c, swings through an arc indicated by the directional arrow 30, to cause further of the material to be displaced therefrom. As the rotation continues the to the position 310d, the hanging portion of the belt member swings, and due to its flaccid nature undulates to still further displace any caked-on material therefrom. The belt member will return to overlaying the corresponding portion of the annular rotary frame member 1102 when it reaches the position of belt member 310e. Depending upon the rotational speed of rotary frame 110, the belt member may “slap” down on the annular rotary frame member 1102, the impact providing a further clearing of any material yet adhered thereto.
Turning now to
Screen clearing assembly 400 may be subdivided into a multiplicity of sets of swinging arm assemblies 410, at least a portion thereof being angularly spaced one set from another. Depending upon the longitudinal extent of the rotary screening apparatus 100″″ groups of sets of swinging arm assemblies 410 may be longitudinally spaced within the cavity 118 in order to provide clearing of all of the screens 116 that enclose the cavity 118.
Each set of swinging arm assemblies 410 include a plurality of swinging arm assemblies 410 spaced longitudinally one from another. The swinging arm assemblies 410 of one set are positioned to be longitudinally offset with respect to the swinging arm assemblies 410 of an adjacent angularly spaced set of swinging arm assemblies. Thus, the mallet members 402a, 402b and 402c of one set of swinging arm assemblies 410 are spaced each from the other a Distance D1. The number of swinging arm assemblies that define a set and the distance D1 therebetween each will depend on the size of the rotary screening apparatus and the propensity of the types of material being screened for forming agglomerations the blind the screens. The mallet members 402d, 402e and 402f of the adjacent angularly spaced set of swinging arm assemblies 410 are likewise spaced each from the other by the Distance D1, but are respectively offset from the corresponding mallet members 402a, 402b and 402c by a distance D2. The distance D2 is smaller than the distance D1 and depends on the number of sets of swinging arm assemblies 410 that are circumferentially spaced within the cavity 118, as well as the propensity of the types material being screened for forming agglomerations the blind the screens.
The plurality swinging arm assemblies 410 that define a set may each be formed by a mallet member of a different length to provide variation in the areas being impacted with respect to a direction transverse to the longitudinal direction of the screens. Thus, the mallet member 402a may have a length dimension L1, the mallet member 402b may have a length dimension L2, and the mallet member 402c may have a length dimension L3, where L1, L2 and L3 are not equal to each other. As yet, no particular advantage has been found for any specific relationship between L1, L2 and L3, but it is contemplated that a particular sequence of mallet member lengths may yet be uncovered that more efficiently clears the screens than other sequences of mallet member lengths. At present, it is preferred to select the lengths of the mallet members to impact the corresponding screen at equal subdivisions of its angular extent. The longitudinal sequence of the various lengths of the mallet member may be arbitrary for a set, with all of the other sets of the screen clearing assembly 400 having the same sequence.
Referring further to
Thus, as the rotary frame 110 rotates about the longitudinal axis, as indicated by directional arrow 10, the head 414 of each mallet member is affected by gravity to be displaced about the pivot pin 422 as a function of their position during the rotation of the rotary frame 110. As illustrated, each mallet member 402a, 402b, 402c of a representative set of swinging arm assemblies 410 remains substantially stationary in a first position as the set of swinging arm assemblies is displaced between the positions 410a and 410b. However, as the rotary frame 110 rotates still further, the mallet members 402a, 402b, 402c, by the time they reach the position of swinging arm assemblies 410c, convert their potential energy derived from the rotating structure to kinetic energy; thereby swinging through respective arcs indicated by the directional arrows 40a, 40b, 40c. The mallet members 402a, 402b, 402c swing from the first position, where the heads 414 thereof are in contact with a leading screen 116, to a second position where the heads 414 of the mallet members 402a, 402b, 402c impact corresponding portions of a trailing screen 116, causing bound agglomerations of the material being screened to be displaced therefrom. The resiliency of the heads 414 results in the mallet members bouncing back through their respective arcs and then impacting the trailing screen 116 again. That process will repeat until all of the converted potential energy has been exhausted.
As the rotation continues to the position 410d, the mallet members 402a, 402b, 402c swing to a position intermediate the first and second positions to hang down into the cavity 118. By virtue of the position of swinging arm assemblies 410d, they regain potential energy. In transitioning from the position of swinging arm assemblies 410d to 410e the regained potential energy is converted to kinetic energy and the mallet members 402a, 402b, 402c swing toward and impact the leading screen 116. Depending upon the rotational speed of rotary frame 110, the mallet members 402a, 402b, 402c will impact the leading screen with sufficient force to provide a further clearing of any material yet adhered thereto. It should be understood that the leading screen was fist impacted by the mallet members of the set of swinging arm assemblies 410 that angularly precede, with respect to the rotation of rotary frame 110, the mallet members 402a, 402b, 402c whose operational cycle was just described. Using
Although this invention has been described in connection with specific forms and embodiments thereof, it will be appreciated if there is modifications other than those discussed above may be resorted to without departing from the spirit or scope of the invention. For example, equivalent elements may be substituted for those specifically shown and described, certain features may be used independently of other features, and in certain cases, particular locations of elements may be reversed or interposed, all without departing from the spirit or scope of the invention as defined in the appended claims.
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|---|---|---|---|
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| 1305685 | Beach | Jun 1919 | A |
| 2086551 | Heller | Jul 1937 | A |
| 4184944 | Tytko | Jan 1980 | A |
| 5605233 | Hauch | Feb 1997 | A |
| 6050423 | Dunnuck et al. | Apr 2000 | A |
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| 6422394 | Page | Jul 2002 | B1 |
