US3358840A

US3358840A - Endless, helical fibre, filtration centrifuge

Info

Publication number: US3358840A
Application number: US581091A
Authority: US
Inventors: Pinkava Jan
Original assignee: Czech Academy of Sciences CAS
Current assignee: Czech Academy of Sciences CAS
Priority date: 1965-09-30
Filing date: 1966-09-21
Publication date: 1967-12-19
Anticipated expiration: 1984-12-19
Also published as: BE721487A; NL6613696A; NL6813910A; DE1782646A1; GB1188620A; FR95632E; DE1632274B1; GB1108407A; AT285461B; DK118279B; BE687630A; CH451019A; SE320935B; US3441144A; CH479334A

Description

Dec. 19, 1967 ENDLESS, Filed Sept. 21, 1966 J. PINKAVA 3,358,840

HELICAL FIBRE, FILTRATION CENTRIFUGE I 5. Sheets-Sheet l I: I: Ki 4 517;: JILL FIG. 1

FIG. 2

INVENTOR. 76 7/ A a u'a ww ih 3,358,840 ENDLESS, HELICAL FIBRE, FILTRATIONICENTRIFUGEY Filed Sept. 21, 1966 J. PINKAVA Dec. 19, 1967 3 Sheets-Sheet 2 mmm m" BEE-.

FIG. 3

" INVENTOR;

Dec. 19, 1967 J. PINKAVA 3,358,840

ENDLESS, HELICAL FIBRE, FILTRATION CENTRIFUGE Filed Sept. 21, 1966 5 Sheets-Sheet 3 INVENTOR. Ja 11 2% K4 u-a United States Patent 3,358,840 ENDLESS, HELICAL FIBRE, FILTRATION CENTRIFUGE Jan Pinlrava, Prague, Czechoslovakia, assignor to Ceskoslovenska akademie ved, Prague, Czechoslovakia Filed Sept. 21, 1966, Ser. No. 581,091 Claims priority, application Czechoslovakia, Sept. 30, 1965, 5,945/65 7 Claims. (Cl. 210-370) ABSTRACT OF THE DISCLOSURE A filtration centrifuge comprising open-ended, ribbed inner and outer drums, the ribs of the inner drum being inside the ribs of the outer drum so that said inner drum is driven by said outer drum, each drum having a hollow shaft, the shaft of the inner drum extending through the shaft of the outer drum, the axes of said drums being skewed so that a fibre introduced through the inner hollow shaft is wound in a helical path through the drums to form a filter surface inside said drums.

The invention relates to a continuous filtration centrifuge.

A continuous filtration centrifuge is known which consists of two ribbed drums inserted one in the other so that their ribs engage into each other. The axes of these drums are concurrent or skewed with respect to each other. The ribs form the envelopes of these drums and their fronts are provided with holes arranged tangentially with respect to the internal surface of the drum; through these holes passes a toroidally wound band of filtration cloth guided over the rounded edge of the outer drum and a roller arranged on its front face, the front face of the inner drum 'being connected coaxially with a shaft passing through at least one swingable bearing arranged in a hollow shaft of the outer drum.

In consequence of the fact that the two axes of the ribbed drums are concurrent or skewed with respect to each other the continuous band of the toroidally wound cloth is transported from the bottom of the drum to its second edge and it returns outside the drum through slots. The mother liquor and the wash waters are centrifuged by the toroidally wound band of filtration cloth whose turns overlap, and the filtered suspension is thrown under effect of the centrifugal force from the edge of the cloth into the respective trough. In consequence of the progressive movement of the band which is arranged in the form of a helix wound on the envelopes of the two drums there is created over the entire internal surface of the drum a coherent filtration surface; consequently, during rotation of the centrifuge the toroidally wound band can be washed and there is continuous centrifugation.

But this centrifuge with a toroidally wound band has no sufiicient filtration capacity for fine suspensions and in some cases it is also difiicult to wash the band.

It is a general object of this invention to eliminate the above mentioned drawbacks.

The invention also relates to a continuous filtration centrifuge. To achieve continuous filtration in this centrifuge there is used a continuous fibre instead of the toroidally wound band. Compared with the known centrifuge, the centrifuge in accordance with the invention uses also a system of two ribbed drums whose axes are also either concurrent or skewed with respect to each other.

The main feature of the invention resides in the following facts; the inner drum is provided with a hollow shaft arranged by means of a bearing in a hollow shaft of the outer drum; outside the centrifuge there is arranged ;a device for driving the continuous fibre which is provided with a motor, and also a winding device which leads the continuous fibre from the inner space of the drums placed one into the other and over guide rollers. From this winding device the continuous fibre is returned to the device for driving the continuous fibre. In consequence of the centrifugal force during running of the centrifuge, the continuous fibre is wound in the form of a helix on the inner surface of the drum which produces a filtration layer for the suspension injected into the inner space of the two drums by a jet arranged near the tube for leading the fibre from the centrifuge.

The invention will be best understood from the following specification to be read in conjunction with the accompanying figures in which:

FIGS. 1 and 2 explain how the fibre is moved on the two drums whose axes are concurrent or skewed with respect to each other;

FIG. 3 illustrates a section through the centrifuge;

FIG. 4 is a cross-section along the line I-II in FIG. 3; and

FIG. 5 illustrates another embodiment of the centrifuge. I

Referring now more particularly to FIG. 1, it is seen that the cylinders 1 and 2 are mounted on axes 4 and 4' which are not parallel. A fibre 3 is wound around the two cylinders. If one of the cylinders, for example cylinder 1, rotates, cylinder 2 is also rotated by the effect of the fibre 3 acting as a sort of belt, and the fibre 3 moves in the direction of the axis 4 of the cylinder 2.

FIG. 2 explains the principle of the invention. g'Ihe two drums 1 and 2 are inserted one into the other and engage one into the other by means of bars or

ribs

5 and 6. If now drum 1 is rotated, it rotates also drum 2. The schematic illustration of FIG. 2 shows that the shaft 4 of drum 1 is hollow and the shaft of the second drum 2 passes therethrough. The bearings 7 of the shafts 4 and 4' can be adjusted slidaibly, and by adjusting one or the other of the bearings the shafts of the two cylinders can be made to extend concurrently. While the two drums 1 and 2 rotate, the fibre moves in the direction of the axis of the drum. The fibre 3 may also be placed on the inner surface of the bars or ribs of drum 2, and if the cylinders move so fast that the fibre 3 is pressed by centrifugal force against the

ribs

5, 6, the fibre moves in the direction of the axes of the two cylinders, and the individual turns of the fibre progressively cover the entire inner surface of the ribs of the cylinders. This creates on the inner surface of the bars a continuous layer of turns of the fibre placed side by side.

FIG. 3 illustrates schematically the arrangement of the entire device, that is a continuous filtration centrifuge, a dosing device and a winding device.

The centrifuge consists of two drums 1 and 2 whose cylindrical surfaces are not continuous or full but are made of

individual ribs

5, 6 which engage into each other, as shown in FIG. 4 which represents a cross-section of the two drums along the line I-II in FIG. 3. Therefore, if drum 1 with the ribs 5 rotates, it carries along the ribs 6 of the drum 2 which is also rotated. The shaft 4 of the drum 1 is mounted in the stationary bearing 7 which is connected with the casing of 29 of the centrifuge. This shaft 4 is hollow, and the second shaft 4' of the second drum 2 passes therethrough. The second shaft 4' is also hollow to guide the fibre inside the drum 2, as will be explained below. The second shaft 4' is mounted in the bearing 8 arranged in the first shaft 4. The second shaft 4 can be shifted in this bearing through a small angle. The shaft 4' is provided with a stationarily mounted ring 9 against which rests on one side a micnornetric screw 10, and on the other side a spring 11. This device makes it possible to swing or shift the shaft 4' against the shaft 4 so that the axes of the two shafts are not parallel, but for example concurrent. The shaft 4 of drum 1 is provided on its end with a belt pulley 12 for driving this drum. Now, if drum 1 is rotated, drum 2 is also rotated due to the fact that the ribs 5 of drum 1 engage with ribs 6 of drum 2, as shown in FIG. 4.

The fibre 13 which is guided into the drum 2 of the centrifuge is wound on the device for driving the continuous fibre. This device consists of two

rollers

14 and 15 on which is placed the fibre which is guided in the manner described below into the inner surface of drum 2 over rollers 16 and via the winding device back to the roller 14 of the device for driving the continuous fibre. The roller 14 is driven by the motor 17 but this movement may also be derived from the drive of the two drums 1 and 2. The fibre is therefore continuous and it is forcedly shifted. The speed of the movement of the fibre produced by the motor 17 can be changed for example in several stages with respect to the speed of the rotation of the drum. Changes of the speed are necesary if it is required to obtain a double or multiple layer of turns of the fibre on the inner surface of the drum 2 of the centrifuge.

In order to facilitate introduction of turns of the fibre into the centrifuge and to overcome the resistance produced by friction on the walls of the hollow shaft 4, it is convenient to insert an ejector between the device for driving the

continuous fibre

14, 15, and the hollow shaft 4'. The ejector 18 directs the movement of the fibre 13 by a concurrent air or water stream so that no disturbances are produced before the fibre enters the hollow shaft 4. The air or Water is supplied into the ejector 18 by a tube 19 in the direction of the arrow shown in the figure. This device permits a smooth creation of the filtration layer even at such rotations of the centrifuge where the centrifugal force acting on the fibre is smaller than the resistance produced by friction of the drawn loop. The fibre is guided from the ejector 18 by the hollow shaft 4' to the bottom of the drum 2, and by action of the centrifugal force it is placed on the inner surface of drum 2. As illustrated schematically in FIGS. 1 and 2, due to the concurrent or skewed arrangement of the two axes or shafts 4 and 4', the individual turns of the fibre are placed close to each other and thus form a. filtration layer 20 comprising turns moving from the bottom of the drum 2 to itsopen end. The fibre 13 is drawn from the raised edge 21 by the tube 22 laying in the axis of the shaft 4 at the open end of the drum 2 via the guiding rollers 16 and the winding device to the device for driving the

continuous fibre

14, 15.

The winding device permits the continuous fibre to be wound off from the drum at any time and to be again wound on into a filtration layer during running of the centrifuge. This winding device consist of two pairs of

rollers

23, 24 arranged freely rotatable on the shaft 25. The

rollers

23, 24 are provided with circumferential grooves. The two shafts 25 are fastened to the frame 26 which is mounted on another shaft 27. The continuous fibre is first wound on one pair of rollers and then in the opposite direction on the other one. Winding on or loosening is achieved by rotation of the entire device about the shaft 27 which is in common to the two pairs of rollers. The fibre passes always from one groove of the upper roller into the next groove of the lower roller and finally it crosses over to the second pair of rollers which rotates therefor in the opposite direction.

It should of course be understood that this device for locating the turns of the continuous fibre during running of the centrifuge may also be replaced by another device performing the same function.

The suspension to be filtered is injected into the drum 2 of the centrifuge by a jet 28 located near the tube 22 through which the fibre is led out from the centrifuge. The centrifuged filtrate (for example a crystal mother liquor, a suspension medium, a dispersion) is captured in a respective part of the casing 29 of the centrifuge and it is led away through the opening 3%, while the filtered rigid material thrown off from the edge of the drum is led away through a trough or a tube 31.

FIG. 5 illustrates another embodiment of the device by means of which the rotating continuous fibre is deviated from the path of the injected suspension. It consists of a tube 32 arranged coaxially with the centrifuge drum in roller bearings which have not been shown in the drawing. The tube 32 is provided on its end with a disk 33 made from a metal, plastic material, glass or another suitable material. The tube 32 is set into rotation in such a manner that its rotations agree with the rotations of the reed of the wound off fibre. The reed is deviated without noticeable friction in the indicated manner so that the suspension can now be sprayed on outside its path. The withdrawn fibre forms a rotating reed which would nor mally cross the stream of supplied suspension which has to be filtered. The suspension is inevitably scattered and the withdrawn fibre is polluted. This is prevented by the device in accordance with FIG. 5.

The disk 33 is set into rotation corresponding to the rotation of the reed of the wound-0E fibre, and after creation of a filtration layer it is inserted as far as possible to the bottom of the centrifuge drum. Thus the rotating reed of the withdrawn fibre is deviated from the path of the sprayed on suspension.

In the stationary state which is created by the function of the centrifuge, a filtration layer is again and again created at the bottom of the drum by winding on the reed, and it is again wound off from the edge of the drum. It is obvious that the fibre returning to the drum can be perfectly freed of remnants of the suspension stuck thereto so that the suspenion is filtrated all the time through a fresh and pure filtration layer. The fibre forms no gaps through which the suspension could flow. If by wrong manipulation a gap is formed, it is suflicient to increase the feed speed of the fibre to close the gap automatically. Before starting filtration, first the necessary filtration layer is formed, whereupon the centrifuge is maintained in the stationary state Where the supply speed (winding-on) of the fibre is the same as the speed of withdrawal (windin oif), and continuous filtration is started by supplying the suspension into the centrifuge.

A multiple layer of the loop is created by a corresponding increase in the supply speed of the fibre which then becomes placed by its individual turns above each other in dependence on the ratio between the speed of supply and withdrawal. For example, if the supply speed of the fibre is three times as high as the speed of withdrawal, there are directly formed triple turns and creation of the filtration layer proceeds otherwise in a normal manner, as when simple turns are deposited.

While the centrifuge is running, the fibre circulates all the time at a certain speed which represents a certain fraction of the circumferential velocity of the centrifuge and, at the same time, the complete layer of turns is moved from the bottom to the edge as a unit by the system of two rod or rib drums engaging into each other. It is obvious from the principle of the centrifuge into which the fibre is placed that the supplied fibre is twisted and wound on the inner surface of the drum, or there occurs twining which is proportional to the difference between the rotations of the centrifuge or the circumferential velocity of the carried fibre, and the speed of its movement through the entire centrifuge. This is no drawback in the case of a continuous fibre because during withdrawal the fibre isalso cut up at the same ratio so that the original twists, if any at all, remain the same outside the centrifuge drum. Washing of the fibre can be arranged at any place between the discharge of the fibre from the drum and its new entry into the drum. Washing is accomplished conveniently countercurrentwise, for example so that the running fibre is led into a tube against a stream of pure Water. If neces sary, the washing water can be returned into the centrifuge to avoid even very small losses.

After washing or, if the fibre is not washed, after the fibre leaves the centrifuge drum, the fibre may be led through another air ejector where it is freed of excess liquid (water or another suspension medium) by a violent stream of air, or of air and a liquid.

It should of course be understood that the various details of the described device may be modified in different manners. For example, the device for driving the continuous fibre may comprise, instead of two groove-d rollers, two or three rollers, of which at least one is provided with a layer of rubber or a similar material, and the fibre is pressed between these rollers and forcedly guided. An other possibility is using a tub-shaped body with a grooved roller. Instead of the described device for Withdrawin g the fibre by means of which the wound-off reed of the fibre is deviated out of the path of the injected suspension, the same result may also be achieved, for example, by synchronized interruption of the spraying-on action at the moment when the moment when the wound-ofl? fibre passes the mouth of the jet. The injector after the wind ingoif device may be replaced .by a pair of wringing rollers. Other details and parts of the device may also be replaced by other parts performing an equivalent function without exceeding the scope of the invention.

What I claim is:

1. Continuous filtration centrifuge, comprising:

an outer drum and an inner drum inserted in the said outer drum;

the envelopes of the said two drums each comprising a plurality of ribs and having their axes arranged with respect to each other in directions different from parallel, and the ribs of each of the two envelopes arranged with respect to each other so that if one of the two drums is rotated, the other is also rotated;

a hollow shaft on said outer drum;

a hollow shaft on said inner drum mounted in the said hollow shaft of the said outer drum;

a device with a motor for driving a continuous fibre;

a winding device which guides the continuous fibre from the inner space of the said two drums to the outside through a tube and over rollers;

means for guiding the continuous fibre back from the fibre winding device to the fibre driving device;

a jet near the said tube through which a suspension can be injected into the inner space of the said two drums onto the filtration layer formed in consequence of the continuous fibre being wound by action of the 1, wherein the said fibre Winding device comprises:

a frame;

two shafts attached to the said frame; pins on which the said frame is mounted; and two grooved rollers freely rotatable on the said shafts attached to the said frame. 5. Continuous filtration centrifuge as claimed in claim 1, wherein the fibre leading away device comprises:

a tube locate-d shiftably in the axis of a centrifuge drum; the end of the said tube lying in the inner space of the said drum being provided with a disk having a smaller diameter than the diameter of the filtration layer formed by the said fibre; means for rotating the said tube at a velocity Whose maximum value equals the velocity at which the said fibre is being wound off. 6. Continuous filtration centrifuge as claimed in claim 4, wherein the fibre leading away device comprises:

a tube located shiftably in the axis of a centrifuge drum; the end of the said tube lying in the inner space of the said drum provided with a disk having a smaller diameter than the diameter of the filtration layer formed by the said fibres; means for rotating the said tube at a velocity whose maximum value equals the velocity at which the said fibre is being wound off. 7. Continuous filtration centrifuge as claimed in claim 6, comprising:

an ejector between the fibre driving device and the hollow shaft of the inner drum; a tube connected with this ejector; means for producing a parallel stream of air and Water and supplying it through the tube and the ejector for directing the movement of fibre.

No references cited.

REUBEN FRIEDMAN, Primary Examiner. F. SPEAR, Assistant Examiner.

Claims

1. CONTINUOUS FILTRATION CENTRIFUGE, COMPRISING; AN OUTER DRUM AND AN INNER DRUM INSERTED IN THE SAID OUTER DRUM; THE ENVELOPES OF THE SAID TWO DRUMS EACH COMPRISING A PLURALITY OF RIBS AND HAVING THEIR AXES ARRANGED WITH RESPECT TO EACH OTHER IN DIRECTIONS DIFFERENT FROM PARALLEL, AND THE RIBS OF EACH OF THE TWO ENVELOPES ARRANGED WITH RESPECT TO EACH OTHER SO THAT IF ONE OF THE TWO DRUMS IS ROTATED, THE OTHER IS ALSO ROTATED; A HOLLOW SHAFT ON SAID OUTER DRUM; A HOLLOW SHAFT ON SAID INNER DRUM MOUNTED IN THE SAID HOLLOW SHAFT OF THE SAID OUTER DRUM; A DEVICE WITH A MOTOR FOR DRIVING A CONTINUOUS FIBRE; A WINDING DEVICE WHICH GUIDES THE CONTINUOUS FIBRE FROM THE INNER SPACE OF THE SAID TWO DRUMS TO THE OUTSIDE THROUGH A TUBE AND OVER ROLLERS;