US2828013A - Sieves and the like - Google Patents

Description

Match 25, 1958 .1. HuRs'r 2,828,013

` v Isliflz AND THE LIKE Filed March sof, 195s e sham-sheet 1 L y r9 J6 jg3/- EN 1,?1 14 I .J 31

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sIEvEs AND THE LIKE Filed Marh 30, 1953 6 Shee'ts-Sheeb` 2 .f2 l lg" 3j .7 1 I I I a '49\ l .5o

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SI1-:VES AND THE LIKE Filed March so, '1953 l e sheets-sheet 4 March 25, 1958 JQ HuRsT 2,828,013

SIEVES AND THE LIKE Filed March so, 1953 s sheets-sheet 5 March 25, 1958 J; HuRsT v2,828,013

` sIEvEs AND THE. LIKE Filed Maren 5o. 1953 e 'sheets-sheet '6 United States Patent SIEVES AND THE LIKE Justin Hurst, Mayfield, England, assignor to Russell Constructions Limited, London, England, a British company Application March 30, 19,53, Serial No. 345,504 Claims priority, application Great Britain August 20, 1952 3 Claims. (Cl. 209--315) The invention relates to the type of sifting apparatus which is described in British patent specification No. 550,661which comprises a series of units each formed of a supporting rim, a gauze, cloth or'like sifting septum stretched over the rim, a tray below the septum to catch fine material, and a second tray below the tray for line material which is connected to an annular wall surrounding the rim of the septum but spaced therefrom so as to catch oversize flowing over the edge, the oversize being directed back to the centre of the apparatus so as to be delivered, if desired, to other units below the Vfirst of similar construction and re-treated, the whole being mounted onY a frame which is capable of a circular motion at high speed and low amplitude in a horizontal plane, usually referred to as gyration (although the term is a misnomer), whereby material can be fed continuously to the uppermost sifting surface and after one or more 1re-treatments the oversize and the fines are collected and continuously discharged. This apparatus is hereinafter referred to as a continuously-operating cascade-type gyrating sieve.'

In the construction described in the aforesaid patent the discharge of fines fromeach tray of the series was effected by a chute which passed out through the side of the unit, but this construction had certain disdavan-V tages. For one thing the discharge chute of each unit extended in an inclined direction close above the sifting surface of the unit below in the series, and this interfered with the possibility of putting anti-clogging brushes on the sifting surface and also with the free circulation of the mass of material lying on the sifting surface. Secondly, assembly and disassembly of the units was made difficult. Such free circulation in a spiral path over the sieve is of greatimportance. struction had the advantagethat each sifting septum formed a continuous surface from the centre to the edge and there was no possibility of accidental admixture of nes and coarse once they had become separated by the `sifting action. Furthermore,A it was possible to mount a tensioning screw at the axis `of the` unit, which screw was capable of being passed through the sifting gauze or the like and of drawing the gauze down in theA centre to put tension on it, which, from the nature of the construction, was bound to be equal along all radii.

It is an object of the present invention to provide a modified `construction of continuously-operating, cascadetype gyrating sieve in which` assembly is easy, internal lateral discharge chutes are obviated, proper free cir-,

-According to the present invention, a continuously-v operating, cascade-type gyrating sieve is characterised by a sifting unitconstruction which comprises a rim, a sifting septum stretched over the rim, means around the edge of the rim to hold the septum and a tray secured At the same time, the con- 2,828,013 Patented Mar. 25, '1958 with a downwardly depending axial discharge-tube for fines, the septum of the lower unit or units having a central opening surrounded by a stilfening ring, which ring and opening are adapted to fit closely around the discharge tube of theV unit above them. In this way the lines are carried through axially to the bottom of the assembly without' opportunity to mix with unsifted material on the upper sideV of. the septum of the lower unit or units, where the 'septum surrounds the discharge tube of the unit above it.` Provision for holding the septum is effected by meansaround the edge of the rim and it becomes possible to" make the assembly of the outer rim,

the septum and the tray of each unit separate from the surrounding wall .which catches oversize to deliver it to the' septum ofthe Aunit below.

The stitfening ring around the central opening of the sifting septum can be so mounted as to be adjustable up or down, to alter the slope and tension of the septum.

The construction makes assembly and cleaning much' easier as thefnec'essityof bringing out a discharge chute foreach unit through the surrounding wall of the unitis obviated.

` It is a further object of the present invention to provide a screen for sifting or filtering purposes which is capable of being mounted in an aperture in a floor which separates an upper from a lower room. According to the present invention a sieve as hereinabove described is taken and is mounted so that the assembly of sifting units is located in the aperture in the floor with the driving motor and supporting frame secured to the ceiling of the room below.' It hasY been found that by the use of a i series of sifting units as described in the aforesaid patent application a very.effective construction for operating inthe position described is obtained, because the'. sifting' being bo'th attached to the bottom of the assembly. The' hopper for the feeding of material to be sifted Vto the ap-v paratus stands conveniently at a low level on the top of the assembly in the upper room, and las the driving motor is in the room below immediately below the ceiling,

it neither interferes with the oor space in the room above nor with the iioor space in the room below.

Conveniently, the feed hopper is supported by flexible struts from the floor of the ,upper room in which it is placed as this assists in maintaining the vibration lin a horizontal plane without undesirable up and down move.-

ments.

The accompanying drawings show certain constructions A in accordance with `the invention Vby' vway :of example.

to the rim` below the septum having a central discharge In the drawings:

Figure l is a diagrammatic sectional view through the sieve assembly.

Figure 2 is 'an enlarged view of part of the structure` of Figure 1.

Figure 3 is a perspective view of a supporting frame' for asieve showing the driving apparatus therefor.

Figure 4 is a` vertical .sectionv of 'analternative con.-

struction intended to besupported from the underside off.

Figure 7 is adetail exploded view, vshowing the method' of securing sifting gauze and of supporting the trays.

Referring to Figures 1,` 2 and. 7,aseries of sifting units is provided each comprising a bowl-shaped collecting tray 11 for fines having acentral vertical dischargetube 12 which. depends `from it. downwardly. The upper. edge of the tray 11 is surmounted by a cast-ring 13 over which is stretched a gauze or cloth A-sifting element or septum 14. Secured to the underside of thetray 1,1.are several'esho'rt spacing-elements 15 which .project downwardly andbelow which is xedan outerbowl-.shaped collectingrtray 16 for oversize. The tray 16 hasa curved. rim 17 which extends upwardly outside thetray 11'and.is spacedtherefrom so that coarse material may `flowover the edge. ofthe gauze into the space between the underside of the tray 11 and the upper side of the collecting tray 16, and be re-directed by tray I16 towards the centre of the apparatus.

The bowl-shape of the trays 11 and 16 is adapted to cause the material to flow readily toward the centre of the trays. `It is found thatthis requires a steeper slope near their ,periphery than nearrtheircentre. The trays are held together by studs 115 which are passed up through the spacing elements 15 and enter tapped holes in the ring 13. The studs have shoulders 116 which engage the tray 11 .and secure it to the ring 13. Nuts 118 below tray 16 secure this tray to the underside of distance pieces 15.

The .collecting .tray for coarse material has la central aperture 18 surrounding the discharge tube 12 of the tray for fines 11 and leaving a sufficient space between its edge and the 'discharge tube 12 for the coarse material to fall freelyon to the siftinggauze of the unit below.V

The curved outer .rim .17 of each of the trays 16 tits into .the'lower portion of a curved outer wall y117 which is extended upwardly in a cylindrical form as shown at 19 and is provided with an'edge curled over a wire 119, t-o t the rim 17 of the unit above it, without, however, being directly fixed thereto.

Each of the gauzes 14 has a central opening large enough to pass the lower end of the downwardly projecting discharge tube y12 of the unit above.v This opening is clamped between a pair of clamping rings 21 in each case and the clamping rings titV closely around the discharge tube 12. The clamping rings have rubber grommets 121 and -are adjustable forheight; to this end they are supported from tray v11 by vlegs 122 and spacers 123. The spacers 123 can be changed for other spacers of similar shape butlonger or shorter as may be required, Yto'adjust the angle of cloth 14.

The outer wall of the topmost unit of the sieves instead of supporting a tray 16 of a further unit above it, supports the rim of a sheet metal hopper 22 and the hopper is clamped down on to the unit by an angle ring 23. The gauze 14 of this unit has its central opening closed by a plate 24 so that mixed pulverulent material 25 fed into the hopper 22 becomes distributed over the surface of the gauze 14.

The lowermost sifting unit of the series has a special nes .collecting .tray 26 which carries an outlet `chute 27. It .alsohasiagspecialouter tray 28 for the coarse material which is provided with a discharge chute 29. The tray 28hasa projecting rib 30 around its vertical wall 19 which rests on the upper edge of a carrier ring 31 forming part of the supporting vframe Vfor the mechanism shown in Figure 2. Around the edge of the carrier ring 31 there are securedtseveral clamping bolts 32 which pass upwardly around the assembly of jsifting units and at their upper ends `pass through lugs 33 on the clamping ring 23. Nuts 34 onzthe bolts 32 -serve todraw the upper clamping ring 23 downwards and grip the whole assembly together.

`By having bolts 32 of .appropriate length fit is possible to assemble any number of these sifting units one above the other, that is'to .say there may be only two such units or there may be three .as shown or-four or even more, as the 1requirements vof the material to be treated may dictate.

'Iherims ,'13 of ;the;trays 11 are yeach formed with a circumferential groove-'35 as shown in the detail, Fig-V ure ,-.7audtthe gauze septum 14 is. rb ent .down over the edge of the rim 13 and held in place by a stout clamping .wire 36 which extends ,all round .thegroove 35 l.andis drawn tight by a tangential nut and screw device 113. In assembling the gauze or cloth 14 on the unit it is first clamped in the centre by rings 21, then lapped over the groove 35 in the rim and the clip 36 placed around it but only partially tightened. Thereafter the cloth is tensioned by pulling it through beneath the clip by means of pincers a little at a time all the way round, and nally theclip is tightened Vto retain the gauze or cloth vfirmly. As will readily be understood, to assist .in tightening:` up the gauze by Athe above described pulling-over operation, the operator can be provided with a jig to hold the parts in .position so vthat/the rings are exactly concentric with the discharge tube 12 below them. It is important that the clamping rings shouldbe concentric with the discharge tube so that the units can readily be built up upon one another without any illiitting of one -on another.

Y The cascade Vsifting unit as 4described above vcan be mounted upon any type desired or gyrating frame. example, it can be mountedron a framehung from Ya. ceilingsuch as that shown in patent specification No. 550,661. Alternatively, itmay be mounted on the frame shownin Figure 3, which comprises a heavy base ring 40 mounted on wheels 41, 42 and carrying three upstanding columns 43. In the centre of the columns 43 is a spider 44 to the centre of which is rigidly bolted an electric motor 45 having a Vertical shaft. The tops of the columns 43 support a ring 46 from which are hung three exiblevsuspension rods 47, located halfway between the columns 43. The suspension rods have at their upper ends rubber mountings enclosed in casings 48 and they are Yconnected through rubber bushes 49 to lugs 50 .at theirlower ends. The lugs 50 are secured to downwardly projecting legs 51 which form part of a gyrating frame. The legs 51 are firmly secured to a casing 52 above the motor 45 and in the casing is an out-of-balance flywheel. The flywheel is driven by the motor through aV exible rubber coupling 53. Above the flywheel casing the legs 51 are splayed outwardly and extends upwardly through the ring 46 without touching it to form arms 54 which carry the ring 31 shown in Figure 1 of the drawing.

It will be noted that in the sifting unit described vthere is no obstruction across the space formed between the underside of each conical tray 16 and the gauze 14 of the unit below it. This space can therefore accommodate cleaning brushes such as have been described in British speciication No. 589,683. There is also space for such brushes below the hopper 22 of the top unit. Moreover the underside of the sifting cloth is also clear of obstruction and if desired, instead of brushes above the cloth a suitable .mounting may be provided for brushes below it.

The units shown in Figure 1 of the drawing are made of thin sheet metal, for example, stainless steel. They are thereforeof light weight and as they are vibrated by the motori45'at a` high speed of the order of 1500 revolutions per minute or more the lightness of weight is a Y material advantage.

Referring now to the construction shown in Figures 4, 5 and 6, the sifting unit assembly including the trays with their outer wall 17, the hopper 22,'the clamping rings 23 and 31 and the clamping bolts V32,V is the same as already described. However, Ythe construction shown in these iiguresditfers in that the sifting unit is-mounted so that it occupies the centre of the space raiorded by anraperture 60 -in the thickness between the floor 61 of an upper room and the ceiling 62 of a room below. Above the vibrating hopper 22 is a liirred hopper 5S.

The apparatus comprises two channel members 63, 64 which are secured ange upwards to the underside of the ceiling 62 of a room in a factory or other location in which theapparatus is to work. These channelmembers are parallel lto one another and located one oneach side .of thecircular aperture 60passing through -the` ceiling tothe :door ofthe room above. Each channel member has secured toit four downwardly depending stiff posts ForY 65 on which isbolted a frame casting 66 having a central aperture 67 (Figure4) which is concentric withjthe' apervibratory frame. The vibratory frame comprises a bot- A tom ring 70 and upwardly extending frame members 71, one for each of the flexible rods, which frame members are secured to the bottom ring and extend upwardly towards the aperture in the ceiling through the centre of the supporting ring 66 which is carried by the channel members 63, 64 below the ceiling.4

Each of the upwardly extending frame members 71 is made of channel-section iron bars bent to shape and near its bottom end carries one of the outwardly extending lugs 69V bolted on to it.

, Referring to Figures 4 and 5,'the`posts 65 in the channel members 6?V are connected to the frame casting 66 by rubber bushes 72 which tend to absorb vibration. The bushes 72 are housed in holes 73 through which the posts 65 pass, but the holes 73 are larger than the posts so as to ensure that the bushes 72 absorb the vibration. In Figure 5 rubber bushes 74 which support the upper ends of the exible rods 68 are visible, spaced around the central opening 67. Intermediately between the rubber bushes 74 are three openings 75 for rigid posts 76 which are bolted at their upper ends to the castings 66 and carry at their lower ends a spider 77 to which is secured an electric motor 78, the lower end of the motor passes through the ring 70 without touching it and carries a guard-plate 80.

The motor shaft 79 is vertical and through a flexible coupling 81 it drives a ywheel shaft 82 which enters a casing 83. In the casing the shaft 82 carries an out-ofbalance flywheel driven by the motor and this causes the structure supported by the liexible rods 68 to vibrate with a circular movement in a horizontal plane. The flywheel casing 83 has lubricant pipes 84 which extend downwardly from it to nipples S5 mounted on the guard-plate $0, so that lubrication of the ilywheel bearing is easy although the casting 66 is closed to the ceiling. The flywheel casing 83 is bolted to the vibrating frame members '7l and above the ywheel casing these frame members are splayed outwardly as arms 86 which carry the afore-described frame ring 31. The top of the assembly of sifting units is approximately level with the oor 61 of the upper room; the base ring 31 is approximately on`a level with the ceiling of the lower room, so that the sifting units occupy the space afforded by the aperture 60 through the ceiling. They do not touch the sides of the aperture 60, however, but are free to move laterally when the tlexible supporting rods 68 flex sideways under the elects of the out-ofbalance weight driven by the motor.

As can be seen from examination of Figure 1, in operating with either of the forms of driving or supporting apparatus above-described the mixed material fed into the hopper 22 flows outwardly over the uppermost sifting gauze 14. Owing to the horizontal circular vibration of the sifting units this material follows a spiral course over the gauze and iine material is caused to fall through the space above the member 11 while coarse material and fines not yet separated flow over the edge into the uppermost of the trays 16. The nest fall to the centre along the inclined walls of the tray 11 the inclination of which must be suicient to ensure this movement notwithstanding the circular vibration. As the centre they fall through the discharge tube 12 and thence to the chute 27.

It is an important feature of the construction in accordance with the present invention that the maximum width of unsupported sifting material (cloth or gauze) is short compared with the total sifting area. For example in the construction shown if the diameter of the sieve is inches inside the ring 13, the maximum radial dimension of the cloth between the clamping rings 21 at the centre and the ring13 issomewhat less thaneight inches. Such a dimension permits of the employment of woven nylon or silk cloth, which is more efficient as a sifting. septum than metal gauze. Owing to the. fact that the material passes through the apparatus in a continuous path which is not interrupted byany projections of such a character as to interfere with the natural spiral circulatory movement imparted by the gyration of the screen, there is no tendency to heap up material atany one point, and the whole screening surface `is eiiicient.

It is important in every case to adjust the slope of the screen so that it gives the best results for the particular material employed, and this vcan easily be done by changing the spacers 123.

. The coarse material from the uppermost tray 16 descends on to the second` gauze 14 where it is further separated from lines. These iines pass again to the centre and to the chute 27 while the oversize passes by the second tray 16 to the third gauze 14 (and so on if there are more units) until finally the coarse oversize, freed from iines, drops into the chute 29. The apparatus operates continuously.

I claim:

l. A continuously operable gyrating sieve comprising in combination a plurality of superposed sifting units each consisting of a circular rim, a sifting septum stretched over said rim, means for gripping the edge of said septum around said rim, a fines-collecting tray beneath said septum having an outer edge joined to said rim, a sealing ring secured to said septum concentrcally with the rim, spacing means securing said sealing ring to the fines tray, the fines tray except in the case of the bottom unit having a downward central discharge tube which tits into and is sealed to the sealing ring of the unit below, an oversize collecting tray located below the nes tray and spaced therefrom, having a rim of greater diameter than the edge of the fines tray and an outer wall section mounted on the rim of the oversize tray and adapted, except in the case of the top unit to tit the underside of the oversize tray and wall unit above it, the bottom unit being provided with discharge chutes for the iines and oversize trays and means outside the wall units to clamp the units together.

2. A continuously operable gyrating sieve comprising in combination a casing for an out-of-balance weight, bracket arms extending downwardly therefrom and carrying attachment means for suspension rods and also extending upwardly therefrom and carrying above the casing a carrier-ring, all said parts constituting a gyrating frame, a fixed frame having a large central aperture to pass the gyrating frame and extending outwards around said aperture in the plane of said casing, liexible suspension rods on the xed frame extending downwardly to said attachment means on the bracket arms of the gyrating frame, an out-of-balance weight in said casing mounted to rotate about an axis parallel with the suspension rods, means for rotating said out-of-balance weight, and, mounted upon the carrier ring, a plurality of superposed sifting units each consisting of a circular rim, a sifting septum stretched over said rim, means for gripping the edge of said septum around said rim, a fines-collecting tray beneath said septum having an outer edge joined to said rim, a sealing ring secured to said septum concentrcally with the rim, spacing means securing said sealing ring to the fines tray, the fines tray except in the case of the bottom unit having a downward central discharge tube which tits removably into and is sealed to the sealing ring of the unit below, an oversize collecting tray located below the nes tray and spaced therefrom, having a rim of greater diameter than the edge of the nes tray and an outer wall section mounted on the rim of the oversize tray and adapted, except in the case of the top unit, to lit the underside of the oversize tray and wall unit above it, the bottom unit being provided with discharge chutes'ffor thenes andloversize trays; and means outside the .wall units towclarnp the units together.

'3. A continuously operable gyrating sieve Acomprising in combination a casing for an out-of-balance Weight, means extending downwardly therefrom to attachment points for suspension rods and upwardlyctherefrom to a carrier ring, said parts constituting apgyrating frame, a xed frame surrounding the gyrating frame, having a central aperture to pass the saine freely and extending outwardly therefrom in the plane of the casing, iexible suspension rods extending downwardly from the fixed frame to said attachment points on the gyratingframe, an out-of-balance weight rotatably mounted vin said casing in the plane of the xed frame, means for rotating said out-of-abalance weight, and a plurality `of vsuperposed sitting units mounted upon and clamped to said carrier `ring, each said unit comprising a ring, a sifting 'said tube being adapted to enter and tit into the sealing ring ofarsirnilar sifting unit mounted below it.

lReferences,Cited inthe le of this patent Y UNITED STATES PATENTS 2,67 6,706

Temple Apr. 27, 1954 2,714,961 Y 'Miller Aug.'9, 17955 Y FOREIGN YPATENTS Y 102,695 Germany Apr. 24, 1899 550,661 Great Britain 12111.19, 1943 574,410 Y Great Britain Ian. 3, 1946

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