US3389855A - Filter - Google Patents

Description

June 25, 1968 v H MLLER 3,389,855

FILTER Grignal Filed May 6, 1963 United States Patent O 3,389,855 FILTER Hans Mller, Erlenbach, Zurich, Switzerland Continuation of application Ser. No. 278,216, May 6, 1963. This application May 23, 1966, Ser. No. 552,340 Claims priority, application Switzerland, May 19, 1962, 6,198/62; Jan. 31, 1963, 1,176/63 8 Claims. (Cl. 233-2) ABSTRACT OF THE DISCLOSURE A centrifuge for separating solid particles suspended in a liquid from the latter, wherein a centrifuging chamber is provided between two plates fixed to the driven shaft of the centrifuge and extending axially spaced from each other transverse to the shaft, and an Vaxially movable tubular member surrounding the shaft and forming with the periphery of one of the plates filter means in form of a narrow annular gap through which the liquid may pass while the solid material will be retained by the gap and will accumulate on the inner surface of the tubular member to be discharged therefrom by moving the tubular member in axial direction so as to open the centrifugal chamber in radial direction.

This application is a continuation of Ser. No. 278,216 filed May 6, 1963, now abandoned.

Centrifuges for separating liquids from solids operate either as decanting centrifuges, where separation is effected by gravity, or as screening centrifuges, where the liquid is pressed by centrifugal force through a screen or fabric on which the solid particles are left behind.

One of the disadvantages of both types of centrifuge is that the separated particles can be discharged from the centrifuging chamber only with diihculty. Either they must be discharged by hand, as in the case of the pendulum centrifuge, or the solid particles are insufiiciently freed from liquid and are deposited in the form of a thick sludge. Continuous discharge, as practised for example with the so-called thrust centrifuge, destroys and crushes the solid particles and can only be used with coarsegrained substances.

A centrifuge has now been found which is free from these disadvantages and which may be designed both as a decanting and a screening centrifuge. In accordance with the present invention, there is provided a centrifuge for separating solids from liquids and having a rotatable shaft, in which two plates fixed to the shaft -form a cavity that serves to accommodate the liquid and that is closed at the periphery by a tubular member, the tubular member being adapted to move in the direction of the axis of rotation so as to enable the cavity to be outwardly opened and closed.

The liquid may be separated simply be decantation or else, as described, additionally by screen centrifuging. In the case of decantation the liquid is separated in the cavity through deflection by means f a partition wall screening the outlet apertures. In the case of screen centrifuging it is done through a narrow filtering gap which preferably parallel the axis of rotation, and the filter gap is cleaned of any separated solids when the cavity is opened by displacement of the tubular closure member.

The invention is illustrated in the accompanying drawings in which:

FIG. 1 shows a section through a centrifuge in accordance with the present invention; and

FIG. 2 shows a section through a modification of the centrifuge.

The basic principles of the centrifuge construction is shown in FIG. 1. Connected to the rotating shaft 300 are 3,389,855 Patented June 25, 1968 ice two disc- like plates 307 and 312 which are spaced a certain distance apart and thus form an annular cavity 301.

The plates 307 and 312 are preferably parallel, although they could also be arranged at a certain angle to one another so that the cavity 301 is trapezoidal. At the periphery of the two plates 307 and 312 is a closure to the outside in the form of a tubular member 310, which can be moved in the direction of the shaft 300. Thus the cavity 301 can be closed and opened by lateral displacement of the member 310. The plate 307 is fixed to the end of the shaft 300, whereas the plate 312 is fixed along its bottom edge to a hollow hub 303 projecting coaxially with the shaft 300 from the plate 307.

Lateral displacement of the closure 310 may be effected mechanically, pneumatically, hydraulically, electrically or magnetically.

If the centrifuge, to which the liquid-solid mixture is fed in direction of the arrow 304 through the hollow hub 303 and passage 306, is used as a decanting centrifuge, then it is equipped with an additional plate 312' extending substantially parallel to the plate 312 .and connected to the outer end of the hollow hub 303. The mixture flows into the moving centrifuge at 306, the heavy solid particles are deposited in the chamber 301, .and the clear liquid flows out of the chamber 301 through a filtration gap 311 formed between the outer periphery of the plate 312 .and the inner surface ofthe member 310.

The liquid fiowing out through the filtration gap, formed between the periphery of the plate 312 and the inner surface of the axially movable tubular member 310, enters an intermediate chamber 308 formed between the plate 312 and the additional plate 312. The plate 312 is formed at a radially inner portion thereof with at least one decanting passage 305 and the additional plate 312' having .a radially outwardly located nozzle outlet aperture 309 and a radially inwardly located overflow aperture 305 forming in plate 312 opening means respectively substantially axially aligned with the gap 311 and the passage 305. The amount flowing through is adjusted s0 as to be greater than the nozzle outlet can cope with. The filtered liquid dams up in the chamber 308 up to the overflow aperture 305' and begins to liow out through the latter. But the damming up in the chamber 308 reduces the differential pressure at the filter gap t0 zero, and no more liquid fiows through the gap. Thus the filter gap 311 is no longer loaded and cannot become clogged. The centrifuge is operated as a decanter until a sufficiently thick cake of residue has formed in the cavity 301, after which the'supply is cut off .at 304. The level in the chamber 308 drops, and the -liquid begins to filter out of the cav-ity 301 into the chamber 308. At this stage, of course, only as -much as the nozzle-or nozzles if several are used-can cope with is filtered. Thus the residue in the cavity 301 is dried through the filtration gap and can then be removed by moving the member 310 towards the right, as viewed in FIG. l, whereby any solid material clinging to the inner surface of the member 310 is stripped from the latter by the annular seal 318 fixed t0 the outer periphery of the plate 307. The member 310 in its closed position engages with a knife edge 310 an annular sealing ring 319 located in a groove of the additional plate 312'.

FIG. 2 shows a centrifuge with a filtration gap mentioned above. A filtration gap 311 is left open between the outer rotating closure plate 312 and the rotating tubular closure member 310, and in many cases is able to replace a filter fabric normally used in centrifuges of this type. The advantage of such a gap is that it is automatically cleaned by centifuging each time the centrifuge is opened. It may readily be used, for example, for separating crystals of a certain size.

The filtration gap is also suitable for so-called silting Y separation. Here, before the liquid to be treated is actually separated in the cavity 301, silting is effected, i.e. before filtration a relatively coarse-grained material used as an aid to filtration is silied in a clean liquid onto the filter surface-in this case onto the filtration gap.

The material 313 forms a previous filtration layer for the medium to be treated. The liquid filtering through is forced outwardly by centrifugal force, i.e. onto the inner wall of the rotating tubular member 310, and accordingly has to pass through the auxiliary filtering layer 313 described. The liquid flows along the inner wall of the rotating member towards the filtration gap 311 and there leaves the centrifuge filtered. As the filtration gap is relatively long, even a very narrow gap of only a few tenths of a millimetre wide will have a broad enough aperture section to let through large amounts of liquid.

The apparatus shown in FIGS. 1 and 2 has proved successful, for example, in decanting and subsequently drying residue from industrial and communal waste water.

The decanting action, as mentioned above, can be improved by fitting certain deliecting means in the actual cavity of the centrifuge, but such an improvement, i.e. an increase in efiiciency, can also be obtained if steps are taken to calm the fiow of liquid through the cavity-by suitable means, and above all to slow down the inwardly directed fiow. FIG. l shows how this can be done.

The partition wall 302 fixed in the cavity 301 should if possible be arranged so as to make the inlet chamber 316 small in comparison with outlet chamber 317. This reduces the speed of flow of the emerging liquid and increases the separation effect.

What is claimed is:

1. A centrifuge for separating solid particulated particles suspended in a liquid from the latter, comprising, in combination, a rotatable shaft; a pair of plates extending transverse to the axis of said shaft and being fixed to the latter axially spaced from each other; a tubular member surrounding said shaft and being axially movable between a closed position overlapping the outer peripheries of said plates and forming therewith a substantially closed centrifuging chamber and an open position opening said chamber in radial direction, one of said plates having an outer diameter slightly smaller than the inner diameter of said tubular member so as to form in the closed position of the latter filter means in form of a narrow annular gap therewith permitting the liquid to pass therethrough while retaining the particulated solid material, whereas the other plate iiuid-tightly engages the inner surface of said tubular member; and passage means communicating with said chamber for feeding solid particulated material suspended in a liquid thereinto.

2. A centrifuge as set forth in claim 1, wherein said shaft has a free end, the other of said pair of plates being fixed to said free end of the shaft and said one plate being located laterally of and beyond said free end of said shaft, and including a hollow hub substantially coaxial with the axis of said shaft and connecting said pair lll 4 of plates to each other, said passage means extending through said hub.

3. A centrifuge as set forth in claim 1, and including a deflector disc in said centrifuging chamber extending in radial direction between said pair of plates axially spaced funher from said one than from said other plate and dividing a radially inner portion of said chamber into a smaller inlet chamber and a larger outlet chamber, said passage means communicating with said smaller inlet chamber.

4. A centrifuge as set forth in claim 1, and including at least one decanting passage extending through said one plate radially inwardly of said filter means.

5. A centrifuge as set forth in claim 4, and including an additional plate axially spaced from said one plate and on the side of the latter facing away from the other of said pair of plates, Said tubular member fluid-tightly engaging in said closed position thereof said additional plate in the region of the outer periphery of the latter to form between said one and said additional plate a pressure-equalizing chamber, said additional plate being formed with opening means respectively substantially axially aligned with said filter means and said decanting passage in said one plate.

6. A centrifuge as set forth in claim 5, and including a deflector disc in said centrifuging chamber extending in radial direction spaced from and between said pair of plates and dividing a radially inner portion of said centrifuging chamber into two flow passages, said passage means communicating with that ow passage which is located between said deliector disc and the other of said pair of plates.

7. A centrifuge as set forth in claim 5, wherein said tubular member has an annular edge face engaging that face of said additional lplate which faces the other of said pair of plates, and including annular sealing means providing a duid-tight seal between said edge face and said face of said additional plate when said tubular member is in said closed position.

8. A centrifuge as set forth in claim 7, wherein said edge face ends in a substantial knife-edge, and wherein said additional plate is provided with an annular groove substantially coaxial with said knife edge, and said annular sealing means being located in said groove.

References Cited UNiTED STATES PATENTS 1,355,559 10/1920 Mauss 233-2 1,588,526 6/ 1926 Cleveland 233-2 1,648,790 lll/1927 Sturgeon 233-46 3,075,693 1/1963 Dega 233-2 FOREIGN PATENTS 588,421 11/1933 Germany. 130,495 2/ 1929 Switzerland.

HENRY T. KLINKSIEK, Primary Examiner.

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