US 1731779 A
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Description (OCR text may contain errors)
Oct. 15, 1929. H, B, HOUSTON 1,731,779
FLoTAToN SCREEN FiledvApIl 9, 41926 www www@ t 5mm/@mam UNITED STATES dPA'IENT orrlcl;d
FLOTATION SCREEN Application led April 9, 1926. ySerial No. 100,816.
This invention relates to screens for flotation processes and the like and its objects are the provision of a generally improved and simpliied screen construction'that may be economically produced and 'which will operate eiiiciently and positively without flexing the screen as a whole and without requiring interconnecting grooves between the apertures or openings through the screen.
The invention is illustrated in the accomn panying drawing in which,
- Figure 1 is a more or less diagrammatic vertical section through an illustrative flotation cell or box showing an embodiment of the present invention in connection therewith; y Fig. 2 is afragmentary section through the screen shown in Figure 1 and on an enlargedscale; and
Figs. 3, 4, 5, 6 and 7 are fragmentary sections similar to Figure 2 and showing a number of different embodiments of the present i'nvention.
Referring to the drawing theiotation box or cell shown is of the type shown in my copending application Serial No. 38,608, filed June 22, 1925. This showing is merely il-` lustrative and it is to be understood that the screen of my present invention has utility in a wide variety of flotation machines and analogous apparatus and that therefore the details of a cell or box, per se, are immaterial and may be varied `as desired.
The cell shown comprises a generally rectangular box 5 having a baffle 6. The pulp may be fed into the box 5 at the left of the baiiie 6, as well understood in the art, and the froth overflows the sides while the tailings may be discharged or withdrawn through a suitable pipe or outlet, not shown.
The screen of Figures 14 and 2 is designated generally at 10 and in the particular embodiment of the invention shown in Figure 1 it constitutes the sloping-bottom of the flotation box or tank 5. Air under the desired pressure and from a suitable source, notshown, is disseminated into fthev flotationpulp 12y through the screen 10, the air,- being brought to the screen 10 by means of suitable conduit `:means '15. The particular conduit' means 15 shown has a` plurality of 'flared outlets 16 for distributing the air beneath the under or inlet side of the screen.
The screen 10 maybe mounted in any suitable or preferred manner. In the particular embodiment shown it is mounted obliquely upon internal ledges 20 to give the sloping bottom effect. The ledges 20 may be scarfed, for example, with the screen 10 set down into the general plane of the ledges and secured as by means of overlying strips 21 secured in place by suitable fastening means 22.
The screen of Figures 1 and 2 comprises a sheet or layer 30 of resilient material mounted upon a rigid backing member 32. The backing member 32 may be formed of hard l rubber, metal or any other suitable or preferred material and the resilient sheet or' layer 30 is preferably vulcanized, cemented or otherwise secured to the backing member 32 at 35 over its entire area. Extending through both the backing member .32 and t-he resilient layer or sheet 30 are a mult-iplicity of apertures 36 and the air stream coming from below or from the inlet side of the .screen is Vdisseminated through these apertures 36 and passes up through the outlet side ofthe screen and into the emulsion above in a great number of small streams or bubbles. v
In the'embodiment of Figures 1 and 2, the apertures or openings 36 are of generally conical formation, decreasing from the bottom or inlet side of the backing member 3.2 of the screen tothe reduced or restricted outlets 38 opening through the upper'surface or outlet side of the resilient sheet or layer 30. The restricted outlets 38 may open directly from the upper surface of the lresilient layer 30 and the enlarged inlets 40 may open di- 90 rectly from the bot-tom surface of the backing member 32 and'there needl be no interconnectedgrooves between the apertures 36 on either side of the screen. i
The apertures 36 are shown in vFigures 1 95 andi 2 as extending vobliquely through the screen, at least, vthey areY in Figures 1 and 2 .obliquely disposed with respect to thejupper or outlet side of the layer 30,'y so`that the Weight the water' and Ore Pulp or other 10 material upon the screen 10 and particularly upon the upper surface of the resilient layer 3() will close the apert-ures 36 when there is no 'air passing therethrough and the closing of the apertures 36 in this manner prevents back leakage of the water or pulp and prevents the water or pulp in detrimental quantities from passing down through the screen to the inlet side.
The resilient upper sheet or layer thereby forms in effect a check valve for closing the apertures 36 against leakage of the pulp or water therethrough. The resilient layer 30 is preferably of relatively soft rubber although any other material having the desired action may be employed. W'hen the air is turned on the pressure thereof overcomes the aperture closing pressure imposed upon the upper surface of the screenv by the water and ore pulp thereon and the air is permittedl to pass freely through the aperture 36 and is disseminated by the screen and issues as bubbles or line streams into the overlying pulp.
In operation, the backing member 32 holds the active area of the layer or sheet- 30 substantially rigid or in substantially fixed position. The apertures 36 may be normally open, i.l e., in the absence of the pressure im posed upon the upper surface of the screen by the weight of the water and pulp thereon or at least said a ertures 36 are opened without flexing the s eet or layer 30 asa whole and without lifting it from the backing member 32 by the pressure of the air on the with the backing member holding said layer 30 rigid or in fixed position as whole and against bodily downward iexing causes an internal compression of the layer 30 and it is this'nternal compression and accompanying internal displacement of the material of the sheet 30 that closes the apertures 36 and im` parts the selfesealing act-ion against downward flow or leakage of the pulp or water through the screen.
In the form of screen of Figures l and 2v the oblique or diagonal disposition 0f the apertures 36 or at least the oblique or diagonal disposition of the upper ends of the apertures 36 withrespect to the top or upper surface ofthe soft rubber or resilient sheet 30 particularly ada ts the sheet 30 for closing the vapertures 36 y the Weightof the overlying thereof and these overlying portions are y forced or compressed down by the overlying material and close the apertures 36 when air is not being passed through the screen. The internal compression of the sheet or layer 30 may also set up a lateral displacement of the material in the sheet which may further aid in closing and sealing the apertures through the sheet. The enlarged inlet 40 facilitates the entry of the air or other fluid under pressure into the apertures from the inlet side of the screen When the air is turned on or a flow of air is set up through the screen.
In the embodiment of Fig. 3, the relatively soft resilient material or soft rubber upper layer of the screen is designated at 42 and the rigid backing is designated at 43. In this case, the apertures through the screen comprise straight or non-conical portions 45 through the relatively soft resilient upper layer and conical portions 46 openin downwardly through the lower layer or acking 43 therefrom and of conical formation providing enlarged inlets 48 at the bottom surface of the backing 43. This gives the upper restricted outlets 45 a somewhat greater length for the self-closing action by the Weights of the overlying material Without sacrificing the enlarged inlets 48 at the bottom surface of the backing 43. The apertures of Fig. 3 are as in the previous embodiment shown as disposed obliquely through the screen. y
In the embodiment of Fig. 4, the apertures 50 are of generally conical formation with the enlarged inlets at the bottom and t-he restricted outlets at the top. In this ease, however, the apertures 50 are shown as extending vertically or perpendieularly through the screen 52. In this ease, the conical formation of the apertures 50 provides some overhang of the upper layer so that upon compression thereof by the overlying weight along with the lateral internal displacement of the materialof the upperl layer which accompanies the compression thereof positively and effectively closes the apertures 50 when air is not being passed through the screen.
In the embodiment of Fig. 57 the apertures 53 are shown in the form of straight holes extending vertically or perpendicularly through the screen 54. lIn this case, there is no appreciable overhang of the material of the upper soft layer and the closing of the apertures 53 is by the internal lateral displacement of the material of the upper'soft layer 55 which is set up by the compression imposed uponthe layer 55 by the overlying material. p
In the embodiment of Fig. 6, thev apertures 58 are in the form of straight openings extending obliquely through the upper layer 59 and lower backing member 60 of the screen. In this case the overhang is again present and the openings are sealed by the `compression and accompanying internal displacement of the material of the upper layer 59 which is caused by the weight of the overlying material when air is not being passed through the screen.
. panying compression of thesheet 63 closes the apertures 62.
I do not intend to be limitedto the precise details of construction nor to the particular l' use or application shown or described.-
tion and against bodily flexing in rection.
1. A flotation screen comprising a layer of resilient material provided with apertures therethrough and mearfs holding the active area of said layer in substantially fixed posieither di- 2. A flotation screen comprising a layer of resilient material, said resilient layer having a plurality of apertures extending therethrough, said apertures being closed by internal displacement of the resilient material and means holding the active area of said layer in substantially fixed position and against bodily flexing in either direction.
3. A flotation screen comprising a layer of resilient material having a plurality of apertures therethrough, said resilient layer being relatively thick and soft to permit opening and closing of said apertures by internal displacement Within the body of theresilient layer and without stretching or bodily7 flexing the resilient layer and means holding said layer against bodily7 flexing in either direction.
4. A flotation screen comprising a layer of resilient material having a plurality of normally open apertures therethrough and means holding said layer against bodily flexf ing in either direction.
5. A flotation screen comprising a layer of rubber having a plurality of apertures therethrough, said layer being of a thickness and softness permitting closing of said aperturesjby internal displacement of the rubber and without'flexing the layer as a whole and means for holding said layer against bodily flexing.
6. A flotation screen comprising a layer of relatively soft resilient material, said layer having a plurality of apertures therethrough and said apertures 'being closed by internal compressionl of the 'resilient material from its normal condition and means holding said layer against bodily flexingin either direction.
7. A flotation screen comprising a rigid backing and a layer of relatively sofiJ resilient material attached to said backing throughout the entire active area of the screen for pre venting bodily flexing thereof, said screen having a plurality of apertures extending through said backing and through said relatively soft resilient layer.
8. A flotation screen comprising a rigid backing having apertures therethrough and a layer of soft rubber attached to said backign throughout the entire active area of the screen for preventing bodily flexing thereof, and having apertures registering with the apertures in said backing. Y
9. A flotation screen comprising a hardy rubber backing and a layer of soft rubber vulcanized to said backing over the active area of the screen, said screen having apertures 'extending through said soft rubber layer and through said backing. l
10. In flotation apparatus the combination of a chamber adapted to contain flotation pulp having a wall of resilient material provided with openings therethru, means for admitting fluid under pressure to the outer side of the resilient wall, said wall being relatively thick and soft with the openings therethru open in the normal condition of the wall, means for holding said wall against bodily flexing, said-openings being capable of being closed by internal displacement produced in the resilient wall by the force of the pulp on one side and being capable of being opened by overcoming, by the pressure of the fluid admitted to the v,opposite side, the internal displacement produced by the pulp.
In witness whereof, I hereunto subscribe my name this 27 day of March, 1926.
v HENRY B. HOUSTON.