US3422955A

US3422955A - Superimposed gyratory sifters

Info

Publication number: US3422955A
Application number: US541647A
Authority: US
Inventors: Walton L Mock; Willie Taylor
Original assignee: SMICO Inc
Current assignee: SMICO Inc
Priority date: 1966-04-11
Filing date: 1966-04-11
Publication date: 1969-01-21
Anticipated expiration: 1986-01-21

Description

Jan. 21, 1969 w. oc ET AL 3,422,955

SUPERIMPOSED GYRATORY SIFTERS Filed April 11, 1966 Sheet of 5 "I F ff 20 k /6 INVENTORS. Vl AL rolv L, Mac/(cf W/"LL/I- Dn LaQ B) T .L E-.- Z W Jan. 21, 1969 W. L. MOCZK ET SUPERIMPOSED GYRATORY S IFTERS Filed April 11, 1966 Sheet fiE.7

WA rg/v L, Mack WILLIE- 72Y40 United States Patent 7 Claims ABSTRACT OF THE DISCLOSURE A sieve device which includes a plurality of superimposed sieves freely suspended on flexible cables and having a motor mounted on the side of the superimposed sieves. The motor is drivingly connected to an eccentric weight which has its vertical axis of rotation disposed in vertical alignment with the superimposed sieves so that the entire assembly is driven in a gyratory motion.

This invention relates to a free-swinging sitting device for industrially sifting large quantities of dry, free-flowing materials. More specifically, but not by way of limitation, the present invention relates to a cable suspended, multidecked industrial sitter having a driving motor for driving the sitter in a gyratory motion, the motor being mounted on the sitter housing and moving therewith during the operation of the sitter.

In industrial sifting apparatus, it is conventional practice to provide a plurality of sieve decks which are stacked or superimposed one upon the other, and which function to provide a large capacity, high throughput separation of dry, free-flowing materials into at least two particle size classifications. These devices generally operate by introducing the particulate material which is to be classified into the uppermost of the superimposed sieves and then, as the sieves are caused to move in a gyratory motion, separating all impurities and particles above a certain panticle size from all of the fines below that particle size, the classified materials being removed from the bottom of the sitter through at least two outlets. Devices of this type are frequently utilized for purifying flour, grains, cereal flakes and other similar materials by the removal of relatively large impurities or foreign objects from the mass of the fluor or grain preparatory to packaging it.

In the operation of sitting devices of the type described, several problems have characteristically been encountered, and attempts have recently been made to overcome these problems by innovations in the design and manufacture of apparatus of this type. One of the problems which persists through all designs to date is that of preventing the operating mechanism, including the motor which drives the sitter in its gyratory motion, from being damaged or rendered inoperative by the vibrating or gyratory motion of the sitter over extended periods of time. It is also important that a balanced gyratory motion be obtained to minimize vibration transmitted to fixed or rigid structure, and to provide a more eflicient sifting action in the apparatus.

To the end of improving the ability of the sitting devices to withstand the gyratory motion imparted thereto over extende periods of operation, it has for some time been the practice to suspend the sitters on flexible supporting members which can yield during the vibratory motion without fracturing or breaking. One type of support for the stacked sieves and the housing in which they may be lo cated is the use of a plurality of flexible reeds which support the stacked sieves, and the housing which may enclose such sieves, at a predetermined vertical height above the floor. As the sitter oscillates or moves with a gyratory motion, these flexible reeds (which are typically constructed of hickory or some other flexible, long-lived wooden material) flex and bend and follow the motion of the sieves and housing. It has also been proposed to suspend the sitter on flexible reeds from a framework or other supporting structure which is rested upon the floor, with such flexible suspension functioning in substantially the same manner as the floor based flexible reeds previously described. In one instance known to me, the proposal has been made to suspend a box sieve type material grading machine on cables from a framework resting upon the floor. This construction is described in McDonald US. Patent 2,399,280.

Although the described flexible suspensions do function to permit greater freedom of movement of the superimposed sieves, and extend the service life of devices of this type considerably, a further problem exists relative to the mounting of the motor and counterweight which are used to drive these stacked sieves and their housing, if one is employed, in a gyrating or circular motion. In sitter devices which are suspended on flexible rods from a floor mounted framework, as shown in Hurst US. Patent 2,848,110, it has been proposed to rigidly mount the motor on the sieve housing supporting framework and to provide a rotating, eccentrically balanced flyweight within the sitter housing. The motor is then drivingly connected to the flywheel through a flexible connection which will permit the position of the flywheel shaft to shift relative to the motor once the device has commenced its gyratory motion. An arrangement of this sort has been found to have the disadvantage of failing to attain the uniformity and smoothness in gyratory motion which is desirable in such devices, particularly at higher speeds. Moreover, the flexible connections which must be provided between the motor and the eccentric weight used to impart the gyratory motion is complicated, expensive and is subject to malfunctioning over extended periods of operation.

The present invention undertakes to provide a high speed, cable suspended, high capacity sitter which includes stacked sieves driven in an oscillatory or gyrating motion by a motor which is carried by, and moves with, the stacked sieves and thus does not require any flexible or yieldable connection between the motor and the eccentric weight or flywheel which is mounted in the sieve assembly and functions to impart gyratory motion thereto. Although the proposal to mount the driving motor on the sieve housing has heretofore been conceived as is depicted is Stoltzfus US. Patent 2,212,818, such arrangements have generally proposed to locate the motor at the bottom of, or beneath the sieve decks, and have thus prevented the withdrawal of the classified solid particulate material from the bottom of the sieve deck. Moreover, mounting of the motor in this location prevents resting the sieve decks and their housing, if one is provided, on the floor when the machinery is disassembled for repairs or shipment.

Broadly described, the present invention comprises a plurality of superimposed sieves or classifying devices which are freely suspended on flexible members, which flexible members are connected at their upper ends to a supporting framework, and which in the preferred embodiment of the invention are braided wire, non-rotating cables; a motor mounted on the side of the superimposed screens; and an eccentric weight driven in rotation by the motor and having its vertical axis of rotation disposed in alignment with the superimposed screens so that the entire screen assembly is driven in a gyratory motion when the motor is energized. In a preferred embodiment of the invention, each of the superimposed screens is positioned within a generally cylindrical housing, and such housing is supported on three cables spaced circumferentially therearound at from each other. It is further preferred to mount the flywheel or eccentric weight, and the motor by which it is driven, in the vertical center of the superimposed screens (that is, with an equal number of screens above and below the motor and flywheel). With this arrangement, a smooth, even gyratory motion is provided, and the assembly transmits minimum destructive vibratory force to the framework, and develops a more eflicient sifting action. Moreover, the described preferred arrangement permits the motor and its associated flywheel to be operated at much higher speeds than it has been possible to develop with the various types of sifter apparatus heretofore in use.

From the foregoing general description of the invention, it will have become apparent that a major and important object of the invention is to provide an improved multi-sieve industrial sifting apparatus which is characterized by an extended operating life, and by a minimum expectation of malfunction and maintenance expenditure.

Another object of the invention is to provide an industrial sifter of the type having a plurality of stacked sieves which can be gyrated or oscillated at higher speeds than have heretofore been considered attainable or safe in sifter constructions of the type previously in use.

An additional object of the present invention is to provide a sifter apparatus which is freely suspended on flexible cables from a fixed overhead structure and which is dynamically balanced during its operation.

Another object of the present invention is to provide an improved forced air pneumatic sifter which can be operated at high speeds and which has a capacity exceeding that of similar sifters heretofore devised.

In addition to the foregoing described objects and advantages, other advantages, meritorious features and objects of the present invention will become apparent as the following detailed description of the invention is read in conjunction with the accompanying drawings which illustrate several typical embodiments of the invention.

In the drawings:

FIGURE 1 is a view inelevation of sifting apparatus constructed in accordance with one embodiment of the present invention.

FIGURE 2 is a view of the apparatus illustrated in FIGURE 1 with the sieve deck housing shown in section to reveal the elements of the apparatus located inside this housing.

FIGURE 3 is a horizontal sectional view taken along line 33 of FIGURE 1.

FIGURE 4 is a horizontal sectional view taken along line 4-4 of FIGURE 1.

FIGURE 5 is a horizontal sectional view taken along line 55 of FIGURE 1.

FIGURE 6 is a perspective view of a different embodiment of the invention.

FIGURE 7 is a view similar to FIGURE 2, but further illustrating the embodiment of the apparatus depicted in FIGURE 6.

FIGURE 8 is a sectional view taken along line 88 of FIGURE 7.

FIGURE 9 is a side elevational view of yet another embodiment of the invention.

FIGURE 10 is a front elevational view of the sifting apparatus depicted in FIGURE 9.

FIGURE 11 is a sectional view taken along line 11-11 of FIGURE 9.

Referring now to the drawings in detail, and particularly to FIGURE 1, the framework 10, which is adapted to be rested upon the floor of a plant or similar installation, includes a plurality of vertically extending frame members 12 which are interconnected at their upper ends by a plurality of horizontal members 14 and rest upon base plates 15. The framework 10 may also include horizontal or transverse brace members 16 interconnecting the vertically extending frame members 12. Suspended within the framework 10 by a plurality of elongated flexible suspension members 18 is a sieve deck housing designated generally by reference numeral 20. In the preferred embodiment of the invention, the suspension members 18 are wire rope cables, preferably of the braided wire, nonrotating type. The cables are connected to the sieve deck housing 20 by a bracket and U-bolt elements 22, and are connected at their upper ends to the horizontal members 14 by similar bracket and U-bolt elements 24. It will be noted in referring to FIGURE 3 that the overall configuration of the housing 20 is cylindrical and that three of the suspension members 18 are connected to the sides of the housing at circumferentially spaced points so that each suspension member is disposed at about 120 around the housing from the adjacent suspension members.

The construction of the sieve deck housing 20 can best be perceived by reference to FIGURES 1 and 2. Thus, it will be noted that the housing 20 includes a generally conically shaped base section 26, a flywheel housing section 28, a sieve section 30 and a lid or cover section 32. The flywheel section 28 and sieve section 30 are generally cylindrical in configuration and carry annular, outwardly extending

flanges

34 and 36 which grip between them a section segregating plate 38. The segregating plate 38 and

flanges

34 and 36 are secured tightly together by means of bolts 40 or other suitable securing means.

The conical base section 26 is provided adjacent its upper edge with an annular, outwardly extending flange 42, and carries a central fines discharge spout 4 4 over which is frictionally telescoped a flexible sylphon connector 4-6. A peripheral overage discharge spout 48 is disposed at one side of the conical base section 26 and is frictionally engaged by a flexible sylphon member 50. A chordally extending partition member 51 isolates the central fines discharge spout 44' from the peripheral overage discharge spout 48. The flange 42 is bolted to a flange 52 carried at the lower edge of the flywheel section 28 and a segregating plate 54 is clamped between the flanges, and isolates the flywheel of the assembly in a manner hereinafter described. It will be noted in referring to FIGURES 1 and 2 that the bracket and U-bolt elements 22 are welded or otherwise suitably secured to the flywheel section 28 of the sieve deck housing 20.

At its upper edge, the sieve section 30 is provided with an annular, outwardly extending flange 56, and a plurality of pivotally mounted C-clamps 58- are used to engage the flange 56 with an annular, outwardly projecting flange 60 carried by the cover section 32, and to lock between the flanges 56 and 60 a segregating plate 62. Centrally disposed in the convexly shaped cover section 32 is a material inlet conduit 64 which is frictionally pressed into a flexible sylphon connector 66.

The prime mover, which in the illustrated embodiment of the invention is an electric motor 70', is adjustably mounted on the flywheel section 28 of the framework 20 by means of bolts 72 and a supporting bracket 74. The motor 70 thus moves with the sieve deck housing 20,

and its position on the housing assures that it will clear the vertically extending frame members 12 during the 'gyratory motion of the housing to be hereinafter described. The drive shaft 76' of the motor 70 is provided with a pulley 78 which drivingly engages a belt 80 which extends through an opening 82 in the peripheral wall of the flywheel section 28.

The arrangement of structure inside the sieve deck housing 2.0 can be best understood by reference to FIG- URES 25 of the drawings. In referring to FIGURES 2 and 4, it will be noted that a plurality of vertically extending guideways 84- are secured to the walls of the sieve deck housing 20 at intervals therearound and serve to guide and align a plurality of generally rectangular sieves 86, which in the illustrated embodiment of the invention are square. Each of the sieves 86 is of conventional construction and forms no part of the present invention except insofar as it is used in combination with the other apparatus herein described. The sieves 86 are superimposed or stacked and function to separate or classify particulate material introduced to the sieve housing 20' through the inlet conduit 64. A top frame 87 carrying hold down straps 88 is placed over the uppermost sieve 86 and is provided with a centrally located inlet conduit sleeve 89 which receives the inlet conduit 64. Hold down rods 90 are used to retain the sieves in their superimposed relation.

In classifying the particulate material, the action of the sieves is to permit the fine materials to pass through a wire grating or screen at the upper surface of each sieve, and to then be deflected by an underlying plate to each side of the sieve, and into a passageway defined between the deck of superimposed screens 86 and the internal surface of the sieve deck housing 20. These passageways are indicated in FIGURES 3 and 4 by reference numerals 91 and communicate with the fines discharge spout 44. The overs or material too large to pass through the sieve screens is ultimately discharged from the surface of the lower sieve into a passageway 92 which is formed between the sieve deck and the housing 20 on the opposite side of the housing from the motor 70. This relatively large material is then discharged through the overage discharge spout 48. This separatory action of the sieves is well understood in the art and will not :be described in greater detail in the present application.

The lowermost sieve 86 in the sieve deck rests upon the section segregating plate 38 which is positioned between the sieve section 30- and the flywheel section 28 of the housing 20. The segregating plate 38 is a disc shaped plate having a circular outer periphery, and having three segments of circles cut away where the segregating plate intercepts the

passageways

91 and 92. Thus, the segregating plate 38 functions to prevent the introduction or infiltration of particulate material into the portion of the flywheel section 28 which contains the flywheel and its driving mechanism, and also prevents passage of particulate material downwardly through the back portion of the housing 20 at which location the belt 80 is positioned.

The flywheel section 28 encloses four horizontally extending

partition members

100, 102, 104 and 106 which are formed in a square array. The partition members 100- 106 thus form a chamber for enclosing the flywheel assembly. The partition member 106 adjacent the side of the sieve deck housing 20 which carries the motor 70 is slotted or partially cut away to provide an opening 108 through which the *belt 80 passes. A counterbalancin g weight 107 for counterbalancing the weight of the motor 70 is secured to the inner face of the partition member 100. Each of the partition members 100-106 is welded at its upper end to the segregating plate 38 and at its lower end to the segregating plate 54. The segregating plate 54 is identical in its configuration to the segregating plate 38 and functions to close the lower side of the flywheel chamber formed by the partitions 100106 while permitting the

passageways

91 and 92 to remain open.

Centrally mounted within the flywheel chamber by attachment to the

partitions

102 and 104 are a pair of elongated, vertically spaced bearing support brackets 112 which support vertically spaced bearing blocks 114. The bearing blocks 114 rotatably journal a flywheel shaft 116 which is keyed to a flywheel 118. The flywheel 118 has eccentrically mounted thereon a weight or mass 120. The belt 80 is passed around the flywheel 118 and functions to drive the flywheel in rotation from the motor Operation In the operation of the embodiment of the sifter apparatus depicted in FIGURES 15, air is forced under superatmospheric pressure, i.e., about 3 p.s.i.g., through the flexible sylphon connector 66 and the conduit 64 into the space over the uppermost sieve 86 of the sieve deck. The air carries with it the particulate material to be separated. Upon commencement of the operation of the sifter apparatus, the motor 70 is energized and drives the flywheel 118 in rotation on the flywheel shaft 116. As the flywheel 118 is rotated, the eccentric mass 120 swings about the axis of rotation of the flywheel and thus imparts through the shaft 116 to the suspended sieve deck housing 20, a gyratory motion which describes a generally circular path within the framework 10.

The gyratory motion of the housing 20 within the framework 10 is permitted by the flexible suspension members 18 which carry the weight of the sieve deck housing 20, and the sieves 86 and driving machinery enclosed therein. Due to the circular configuration of the sieve deck housing 20, it can be conveniently and beneficially suspended by a three point support upon the suspension members 18, and this feature permits its gyratory motion to encounter less resistance, and to be of more uniform velocity nad more symmetrical motion than can be realized when a square or box-type sifter is utilized, and is suspended upon reeds or flexible wooden support members. This is particularly true when it is undertaken to support the sieve deck housing by flexible support members extended upwardly from the floor.

It is to be further noted that the motor 70, in being mounted directly on the sieve deck housing 20, moves with the sieve deck housing and follows precisely its gyratory motion. The distance between the belt pulley 78 and the flywheel shaft 116 thus remains constant, and the tension in the belt also remains constant. No unbalanced stresses are thus imparted to the power connection between the motor 70 and the flywheel 118, and the flexible suspension members 18, particularly where the preferred braided wire, nonrotating cables are utilized, damp out and absorb substantially all of the vibratory, as well as gyratory, motion imparted to the framework 20 by the motor 7 0.

Upon entering the sieve deck housing 20 from the sylphon connector 66, the velocity of air moving through and around the sieves is greatly reduced from the velocity of air moving in the flexible sylphon connector 66 and the conduit 64. The particulate material thus may be said to move downwardly through the sieve deck primarily due to the influence of gravity rather than by any substantial air velocity which moves the particles. Upon contacting the upper screen surface of the first sieve 86, many of the relatively fine particles of the material pass through the screen, and the remainder of the fines plus the overs or coarse particles to be utimately separated gravitate through a large slot at one end of the uppermost sieve and onto the screen of the sieve which is located next below the uppermost sieve. The fines which have passed through the screen of the uppermost sieve are deflected by a V-shaped lplate (not seen) out the two opposite sides of the sieve and into the two passageways 91 located at opposite sides of the sieve deck housing 20. The overs or coarse particles with some fines entrained continue to pass downwardly from sieve to sieve, with more and more fines being separated therefrom by each sieve and deflected into the passageways 91 until the final overage fraction of relatively coarse particles is passed out of the front end of the bottom sieve and into the passageway 92. From the passageway 92, the coarse overage leaves the housing 20 by way of the overage discharge spout 48 and the sylphon connector 50. In passing from the relatively large volume inside the housing 20 into the restricted

volume conduits

44 and 48, the moving air increases in velocity so that movement of the separated or classified particles out of the sifting apparatus is air assisted, and the air conveying system can be utilized without diversion of air from the sieve deck housing 20, or the inclusion of complicated valving for moving the particulate material into and away from the assembly.

By the employment of the cable suspended, cylindrical sieve deck housing 20 and the mounting of the driving motor 70 on the side of the housing, a smoother gyratory motion can be obtained, and less stress imparted to the several parts of the apparatus as a result of vibration, than has been attainable in devices of this general type heretofore in use. The apparatus is characterized by an 7 extended operating life, and is highly eflicient in its separatory action.

A modified embodiment of the invention is illustrated in FIGURES 6, 7 and 8. In this embodiment, a framework 10 is again provided, and includes the vertically extending frame members 12, and horizontal memebrs 14 and the braces 16 hereinbefore described. The sieve deck housing which is provided in this embodiment of the invention is generally rectangular in configuration, and is designated generally by reference character 130. The housing 130 includes two side walls 132, a back wall 134 and a front wall formed predominantly by a removable door 136. The door 136 is retained in position on the framework by pivotal dogs 138. The sieve deck housing 130 is suspended in the framework 10 by means of a plurality of flexible suspension members which, in the illustrated embodiment, take the form of wire rope cables 140. As depicted in FIGURE 6, the sieve deck housing 130'is suspended by four cables which are each doubled over a fixed arcuate guideway 142 located at the top of the framework, and secured to the horizontal members 14. It will be noted that the ends of each cable 142 are secured at approximately the center of the housing 130 by means of bracket and U-bolt elements 144. The sieve deck housing 130 is provided with a cover plate 146 which carries a central inlet conduit 148, and with a bottom plate 150 which is provided with a coarse material or overage outlet 152, and a pair of fine material outlets 154 located on opposite sides of the housing 130 and only one of which is visible in FIGURES 6 and 7.

Centrally disposed within the housing 130 is a flywheel chamber designated generally by reference numeral 156. The flywheel chamber 156 is defined by a bottom panel 158, a top panel 160, a pair of side panels 161, and a pair of

end panels

162 and 164. It will be noted that the end panel 164 is provided with an aperture 166 which is aligned with an aperture 168 formed in the back wall 134 of the sieve deck housing 130. A prime mover counterweight 169 is secured to the panel 162.

A flywheel assembly designated generally by reference numeral 170 and substantially identical in construction to the flywheel assembly used in the embodiment of the invention illustrated in FIGURES 15 is mounted within the flywheel chamber 156 for rotation about a vertical axis on a shaft 171. The flywheel of the flywheel assembly is driven in rotation by a belt 172 which extends between the flywheel and a pulley 174 carried by a prime mover which is preferably an electric motor 176 as depicted in FIGURE 7. The electric motor 176 is adjustably secured by a suitable bolt and bracket assembly 178 to a mounting board 180 which extends transversely across the back of the sieve deck housing 130 and is secured to the back wall 134 thereof. Thus, the motor 176 is mounted on, and moves with, the housing 130 and a constant spatial relationship is maintained between the motor and the flywheel assembly 170.

Disposed within the sieve deck housing 130 and both above and below the flywheel chamber 156 are a plurality of superimposed sieves 180. Disposed immediately below the bottom panel 158 of the flywheel chamber 156, and between this panel and one of the sieves 180 is a hollow spacing frame 184. The removable door 136 is provided with an inclined deflection plate 188 which extends between the door and the sieve below the spacer frame 184, and functions to deflect overage from the first sieve 180 above the flywheel chamber 156 into the sieve immediately below the spacer frame 184.

The sieves 180 and the spacer frame 184 are all removable from the sieve deck housing 130 through the opening provided at the front of this housing when the door 136 is removed. As will be understood by those skilled in the sifter art, each of the sieves 180 is of lesser dimension than the distance between the side walls 132 of the sieve deck housing 130 so that passageways 185 are defined between the opposite sides of the sieves and the side Walls of the housing. The side walls 161 of the flywheel chamber 156 are also spaced inwardly from the side walls 132 of the sieve deck housing so that a continuous unobstructed passageway exists from the uppermost sieve to the discharge conduits 154 which receive the fines separated by the sifting apparatus, The overs or relatively coarse material from each sieve 180 gravitates from one sieve into the next sieve therebelow, and pass in a sinuous front to back, then back to front movement through the several sieves in the upper portion of the housing 130 until thesieve immediately above the flywheel chamber 156 is reached. At this point, the overs or unsifted material from this sieve is passed out of an open end of this sieve into an open space defined between the removable door 136 and the aligned front surfaces of the flywheel chamber 156 and the stacked sieves 180. This overage material gravitates in the space 190 until it strikes the deflection plate 188, and is deflected back into the sieve 180 disposed immediately below the spacing frame 184. The overage material is then circulated through the three superimposed sieves in the lower portion of the sieve deck housing 130 until it is finally: discharged into a space 192 at the bottom of the housing and communicating with the overage discharge conduit 152.

It will be noted in referring to FIGURE 7 that an equal number of sieves are provided both above and below the flywheel chamber 156 and that, accordingly, there is a fairly equal distribution of weight on opposite sides of the flywheel assembly 170. The flywheel is thus disposed at substantially the center of gravity of the suspended mass which includes the sieve deck housing 130 and all of the elements which it encloses. The motor 176 is counterbalanced by the weight 169 which is secured to the front panel 162 of the flywheel chamber 156. Thus, the sifting apparatus is substantially balanced dynamically.

The operation of the embodiment of the invention depicted in FIGURES 6-8 is similar to that of the FIG- URES 15 embodiment in that the motor 176 drives the flywheel assembly 170 to move the eccentric mass forming a part thereof in rotation about a vertical axis. This rotating eccentric weight then imparts a gyratory motion to the suspended sieve deck housing 130, and the sieves which it carries, which motion effectively sifts and classifies the particulate material passed from top to bottom of the housing through the several superimposed sieves. The swinging or gyratory motion of the sieve deck housing 130 is absorbed by the cables 140, and little or none of the gyratory motion and random vibration setup in the apparatus is transmitted to the framework 10. This embodiment of the invention presents the advantage with respect to that depicted in FIGU-RES 15 of being more perfectly balanced dynamically in that it provides for the location of the flywheel assembly 170 and the driving motor 176 at approximately the center of gravity of the suspended portion of the apparatus.

Yet another embodiment of the invention is illustrated in FIGURES 9-11. This embodiment depicts the principles of the invention as they are applied to a so-called boxless type sifting apparatus in which the several sieves are superimposed upon each other in a vertical stack, but are not enclosed within any type of sieve deck housing. The passage of material in the sieves from the inlet to the several outlets is accommodated by a plurality of passageways located internally of the several sieves, and a relatively tight seal is maintained between the adjacent sieves in the stack so as to prevent the undesirable loss of material during the use of the apparatus. Boxless type Sifters of the described construction are widely used in the sifting technology, and except for the incorporation in combination therewith of the flywheel driving system and the flexible suspension, constitute no part of the present invention.

In this embodiment of the invention, a framework 200 is provided and includes vertically extending stanchions 202 which are interconnected at their upper ends by horizontal members 204 and diagonal braces 206. Suspended within the framework 202 on a plurality of flexible suspension members 208, which are preferably braided wire, non-rotating cables, are a plurality of mated, superimposed sieves 210. The sieves 210 are of square configuration and of identical size, and may be retained in their superimposed position by dowel pins, or by a plurality of swinging strap members 212 or both. The uppermost sieve 210 is provided with a cylindrical inlet conduit 214. The lowest sieve 210 in the sieve deck rests upon a flywheel housing indicated generally by reference numeral 216.

The flywheel housing 216 includes a pair of side plates 218, a front plate 220 and a rear plate 222. Disposed within the side plates 218, front plate 220 and rear plate 222 is an internal housing which includes a forward plate 224 extending parallel to, and spaced from the front plate 220 of the flywheel housing, and two spaced side plates 226 which are each spaced inwardly from, and extend parallel to, the side plates 218 of the flywheel housing. There are thus defined between the internal housing formed by the

plates

226 and 224 and the flywheel housing 216, a pair of fine material passageways 230 which are disposed at opposite sides of the flywheel housing, and an overage or coarse material passageway 232 which is disposed at the front or forward portion of the flywheel housing 216. The line material passageways 230 each communicate with a discharge duct 236 and the coarse material or overage passageway 232 communicates with a coarse material discharge duct 238.

Welded or otherwise suitably secured to the side plates 2.18 of the flywheel housing 216 are two pairs of spacer plates 240. Each pair of spacer plates 240 supports an anchor plate 242 through which are passed adjustable U- bolts 244 for the purpose of clamping or gripping the lower ends of the cables 208. The upper ends of the cables 208 are retained in suitable securing elements 246 mounted on the horizontal members 204 at opposite sides of the framework 200. An electric motor 248 is adjustably mounted on the flywheel housing 216 by a bracket and bolt assembly 250 and drivingly engages an endless belt 252 which passes around the flywheel of a flywheel assembly 256 mounted in the flywheel housing 216 in the manner hereinbefore described. The flywheel assembly 256 includes an eccentrically mounted mass or weight 258 which functions, when the flywheel is rotated in the manner hereinbefore described, to impart a gyratory motion to the cable suspended portion of the sifter apparatus.

The embodiment of the invention depicted in FIG- URES 9-11 functions similar to the embodiments of the invention which have been previously described. Thus, upon the commencement of the gyratory motion of the suspended portion of the apparatus, including the stacked sieves 210, and upon the introduction of particulate material to be classified to the stacked sieves through the inlet conduit 214, screened or separated fine material from each of the sieves is permitted to gravitate through vertical passageways located within the sieves 210 at opposite sides thereof until such separated fine material enters the two discharge ducts 236 disposed below the flywheel housing 216. The coarse material or overage moves from sieve to sieve until the final overage product is deposited in the space 232 at the forward end of the flywheel housing 216, and from this point passes into the coarse material discharge duct 238.

As in the other embodiment of the invention, the location of the motor 248 and the flywheel assembly 256 in substantially the same horizontal plane as the points of connection to the suspended portion of the apparatus in the lower ends of the cables 208 permit better dynamic balance to be achieved in the apparatus. Moreover, in suspending the sieve deck on the flexible, braided wire, nonrotating cables 208 and mounting the motor 248 on the flywheel housing 216 for movement therewith, very little vibrational stress is transmitted to the framework, and there is no need to provide a flexible or yielding connection between the motor and the flywheel.

From the foregoing description of the invention, it will have become apparent that the present invention provides an improved sifting apparatus which, due to its dynamic balance, the use of highly flexible suspension members, and the mounting of the motor on the suspended portion of the apparatus, can be operated at high speeds, and is characterized in having greater durability and a longer service life than has been attainable With apparatus of this type is heretobefore proposed. The sifter apparatus of the invention can be relatively economically constructed and maintenance costs over extended periods of time are reduced because of the mechanical stability of the apparatus, and its substantial structural strength.

Although several embodiments of the invention have been depicted in the drawings and described in the foregoing specification in order to provide examples of how the basic principles of the invention are utilized with specific apparatus, it will be immediately understood that several equivalent structures could be provided without departure from the basic principles which have been herein set forth. It is further to be pointed out that though several isolated and individual features which are utilized in the structural combinations hereindepicted have been employed in various prior art sifting devices, it has not, to our knowledge, been proposed to use the combinations of structure which are herein depicted and hereinafter claimed, and we have found that such combinations yield results which are not to be expected by an extrapolation of the several isolated effects of these individual features as they were obtained and recognized in prior art devices used for the purpose of sifting particulate materials. In any event, any functionally equivalent structures which continue to rely upon the basic principles herein enunciated, but which depart in minor respects from the apparatus which we have shown and described, are considered to be circumscribed by the spirit and scope of this invention except as the same may be limited by the appended claims or reasonable equivalents thereof.

We claim:

1. A sifting apparatus for classifying solid particulate materials comprising:

a vertically extending, rigid framework having a plurality of horizontally spaced, vertically extending members, and having horizontal members interconnecting the upper ends of said vertically extending members;

a plurality of elongated, flexible suspension elements each connected at one of its ends to at least one of said horizontal members and depending downwardly therefrom;

a plurality of vertically stacked sieves connected to the lower ends of said elongated, flexible suspension elements and supported thereby for free swinging movement within said framework;

means for introducing a mixture solids to be sifted to the upper side of the uppermost one of said vertical ly stacked sieves;

means for separately withdrawing from the lower side of the lowermost one of said vertically stacked sieves, a fines portion and a separate coarse portion of a mixture of solids to be sifted, said means for introducing a mixture of solids to be sifted to the upper side of the uppermost one of said vertically stacked sieves and said means for Withdrawing portions of said mixture from the lower side of the lowermost one of said vertically stacked sieves being vertically aligned;

a prime mover mounted on, and movable with, said vertically stacked sieves at a location thereon which is horizontally aligned with the lower ends of said suspension elements and which is on the outside of said sieves and horizontally spaced from the vertical axis thereof, said vertical axis being substantially equidistantly spaced from said suspension elements, and said prime mover being entirely free of said framework and movable with said stacked sieves relative to said framework;

means for imparting a gyratory motion to said vertically stacked sieves mounted on said sieves for rotation about said vertical axis, said means for imparting a gyratory motion to said vertically stacked sieves being disposed at a location substantially in horizontal alignment with said prime mover and the lower ends of said suspension elements, and being aligned with said vertical axis and said means for introducing said mixture and for withdrawing portions of said mixture;

means drivingly interconnecting said prime mover and said means for imparting a gyratory motion to said vertically stacked sieves; and

means for by-passing said materials around said means for imparting a gyratory motion to said vertically stacked sieves whereby said mixture of solids to be sifted can pass from said means for introducing said mixture to said means for separately withdrawing a fines portion and a separate coarse portion of said mixture.

2. Sifting apparatus as defined in claim 1 wherein said flexible suspension elements comprise three equidistantly spaced wire rope, non-rotating cables connected between said horizontal members and said stacked sieves.

3. A sifting apparatus as defined in claim 1 and further characterized to include a generally cylindrical rigid housing enclosing and supporting said vertically stacked sieves, and wherein said elongated flexible suspension elements are connected at their lower ends to said housing and said prime mover is secured to the outside of said housing for movement with said housing and the stacked sieves enclosed therein.

4. A sifting apparatus as defined in claim 1 wherein said means for imparting a gyratory motion to said vertically stacked sieves comprises:

a rotating member mounted on said sieves for rotation about said vertical axis; and

an eccentric mass carried by said rotating member.

5. A sifting apparatus as claimed in claim 4 and further characterized to include a counterbalancing weight for counterbalancing the weight of the prime mover and located on the opposite side of the axis of rotation of said rotating member from said prime mover.

6. A-sifting apparatus as defined in claim 4 wherein said sieves are rectangular, and said apparatus further includes a cylindrical housing enclosing said sieves and supporting said prime mover on the outside thereof, said housing comprising:

a material inlet opening at the upper end thereof constituting said means for introducing a mixture of solids;

at least two discharge openings at the lower end thereof constituting said withdrawing means; and

said housing being spaced from the sides of said stacked sieves and defining therewith vertical channels for accommodating the passage of separated portions of said mixture through said housing and around at least some of said sieves.

7. A sifting device as defined in claim 6 wherein said flexible, suspension elements comprise three elongated, flexible, wire rope, non-rotating cables spaced equidistantly from each other and each having a lower end secured to said housing at substantially the same horizontal level as the position of mounting of said prime mover.

References Cited UNITED STATES PATENTS 43,318 6/1864 Low 209-275 1,267,562 5/1918 Lindsay 209366 X 2,212,818 8/ 1940 Stoltzfus 209332 2,335,084 11/1943 Rice 209363 X 2,587,498 2/1952 Marsh 209-319 X 2,634,617 4//1953 Dryg 209366.5 X 2,705,561 4/1955 Denovan 209332 2,848,110 8/1958 Hurst 209332 FOREIGN PATENTS 462,228 3/1951 Italy.

HARRY B. THORNTON, Primary Examiner.

R. HALPER, Assistant Examiner.

US. 01. XR.