Process and apparatus for filtering suspensions

Claim 3

The method of claim 1, wherein the cycle of applying the suspension to the exterior of the filter, interrupting the application of suspension, continuing the rotation of the filter with the pressure in the interior thereof maintained below the pressure exteriorly of the filter, and removing from the filter the material of reduced liquid content is repeated.

Claim 4

The method of claim 2, wherein the peripheral velocity of said filter and the differential between the pressures in and exteriorly of the filter are maintained constant throughout the plurality of filtering cycles.

Claim 5

The method of claim 1, wherein the filter is rotated at a speed such that the peripheral velocity of said filter is in the range of from 0.5 to 2 meters per second.

Claim 8

The method of claim 5, wherein the cycle of applying the suspension to the exterior of the filter, interrupting the application of suspension, continuing the rotation of the filter with the pressure in the interior thereof maintained below the pressure exteriorly of the filter, and removing from the filter the material of reduced liquid content is repeated.

Claim 9

Apparatus for filtering suspensions which comprises: a hollow, cylindrical, rotary filter; means for effecting continuous rotation of said filter about a horizontal axis; means operable while said filter is rotating to maintain the pressure within said filter at a level below the pressure exteriorly of the filter and thereby create a force capable of effecting the eduction of liquid from the exterior of the filter through said filter to the interior thereof; means for applying the suspension to be filtered to the exterior of the filter and for terminating the application of the suspension to the filter when a layer of at least a selected minimum depth has been formed thereon which includes a reservoir subjacent said filter and means capable of effecting relative vertical movement between said rotary filter and said reservoir for first so adjusting the distance between the suspension contained in said reservoir and said filter that said filter will contact said suspension as the filter rotates and then so adjusting said distance as to prevent contact between said filter and the suspension thereon with the suspension in the reservoir; means operable after the application of the suspension to the filter has been terminated and while the application of suspension to said filter is interrupted to continue the rotation of the filter through at least one revolution while maintaining the pressure within the filter at a level below the pressure exteriorly thereof so that the liquid content of the material applied to the exterior of the filter can be reduced to a selected level by the eduction of liquid from said layer through the filter to the interior thereof; and means operable entirely after the formation of the layer on the filter has been completed and the liquid content of the material has been reduced to the selected level and while the application of the suspension to the filter is interrupted for removing material of reduced liquid content from the exterior of the filter, whereby the removal of liquid from the layer of material on the filter can be made independent in length of time from the formation of said layer thereon.

Claim 10

Apparatus for filtering suspensions which comprises: a hollow, cylindrical, rotary filter; means for effecting continuous rotation of said filter about a horizontal axis; means operable while said filter is rotating to maintain the pressure within said filter at a level below the pressure exteriorly of the filter and thereby create a force capable of effecting the eduction of liquid from the exterior of the filter through said filter to the interior thereof; means for applying the suspension to be filtered to the exterior of the filter and for terminating the application of the suspension to the filter when a layer of at least a selected minimum depth has been formed thereon which includes a reservoir subjacent said filter and means capable of effecting relative vertical movement between said rotary filter and said reservoir for first so adjusting the distance between the suspension contained in said reservoir and said filter that said filter will contact said suspension as the filter rotates and then so adjusting said distance as to prevent contact between said filter and the suspension thereon with the suspension in the reservoir; means operable after the application of the suspension to the filter has been terminated and while the application of suspension to said filter is interrupted to continue the rotation of the filter through at least one revolution while maintaining the pressure within the filter at a level below the pressure exteriorly thereof so that the liquid content of the material applied to the exterior of the filter can be reduced to a selected level by the eduction of liquid from said layer through the filter to the interior thereof; and means operable entirely after the formation of the layer on the filter has been completed and the liquid content of the material has been reduced to the selected level and while the application of the suspension to the filter is interrupted for removing material of reduced liquid content from the exterior of the filter, whereby the removal of liquid from the layer of material on the filter can be made independent in length of time from the formation of said layer thereon.

Claim 11

The apparatus of claim 7, wherein the filter is vertically immovable and including a fluid-actuatable motor for supporting and moving said reservoir up and down relative to said filter to effect the relative vertical movement therebetween.

Claim 12

The apparatus of claim 7, together with means for limiting the level of the suspension in the reservoir which includes a conduit through which the suspension to be filtered can flow into said reservoir, valve means in said conduit, and means including a float in said reservoir for so controlling the opening anc closing of said valve that said valve will be and and the flow of the suspension into said reservoir interrupted when said filter is out of contact with the suspension in the reservoir.

Claim 13

The apparatus of claim 7, wherein the means for removing material of reduced liquid content from the exterior of the filter comprises a slide, a knife means pivotally mounted on said slide, means operable when the liquid content of the layer of material on the filter has been reduced to the selected level for pivoting said knife means relative to said slide to an operative position in which said knife means is engageable with the layer of material on the exterior of the filter to remove material therefrom and for thereafter pivoting said knife means to an inoperative position in which the knife means is isolated from said layer of material, and means for moving said slide and said knife means toward and away from said filter to thereby control the depth to which the material is removed from said layer by said knife means.

Claim 14

The apparatus of claim 7, wherein the means for removing material of reduced liquid content from the exterior of the filter comprises a knife means, a base means, means supporting said knife means from said base means, motor means mounted on said base means for moving said knife means between an operative position in which said knife means is engageable with the layer of material on the exterior of the filter to remove material therefrom and an inoperative position in which said knife means is isolated from said layer of material.

Claim 15

Apparatus for filtering suspensions which comprises: a hollow, cylindrical, rotary filter; means for effecting continuous rotation of said filter about a horizontal axis; means operable while said filter is rotating to maintain the pressure within said filter at a level below the pressure exteriorly of the filter and thereby create a force capable of effecting the eduction of liquid from the exterior of the filter through said filter to the interior thereof; means for applying the suspension to be filtered to the exterior of the filter; means for interrupting the application of the suspension to the filter when a layer of at least a selected minimum depth has been formed thereon; means for thereafter and without the application of additional suspension to said filter, continuing the rotation of the filter while maintaining the pressure within the filter at a level below the pressure exteriorly thereof, whereby the liquid content of the material applied to the exterior of the filter can be reduced to a selected level by the eduction of liquid from said layer through the filter to the interior thereof; and means for removing material of reduced liquid content from the exterior of the filter which comprises knife means which has a cutting edge and which is movable between an operative position in which the knife means is engageable with the layer of material on the filter and an inoperative position in which the knife means is isolated from said layer and a scraper means engageable with said knife means as the latter is moved from the operative to the inoperative position thereof to displace from said knife means material removed from the rotary filter and adhered to said knife means, said scraper means also being engageable with said cutting edge as said knife means is moved towards said inoperative position to thereby hone said cutting edge and keep it sharp.

Claim 16

Apparatus for filtering suspensions which comprises: a hollow, cylindrical, rotary filter; means for effecting continuous rotation of said filter about a horizontal axis; means operable while said filter is rotating to maintain the pressure within said filter at a level below the pressure exteriorly of the filter and thereby create a force capable of effecting the eduction of liquid from the exterior of the filter through said filter to the interior thereof; means for applying the suspension to be filtered to the exterior of the filter; means for interrupting the application of the suspension to the filter when a layer of at least a selected minimum depth has been formed thereon; means for thereafter and without the application of additional suspension to said filter, continuing the rotation of the filter while maintaining the pressure within the filter at a level below the pressure exteriorly thereof, whereby the liquid content of the material applied to the exterior of the filter can be reduced to a selected level by the eduction of liquid from said layer through the filter to the interior thereof; and means for removing material of reduced liquid content from the exterior of the filter which comprises knife means which has a cutting edge and which is movable between an operative position in which the knife means is engageable with the layer of material on the filter and an inoperative position in which the knife means is isolated from said layer and a scraper means engageable with said knife means as the latter is moved from the operative to the inoperative position thereof to displace from said knife means material removed from the rotary filter and adhered to said knife means, said scraper means also being engageable with said cutting edge as said knife means is moved towards said inoperative position to thereby hone said cutting edge and keep it sharp.

Claim 17

The apparatus of claim 12, wherein said scraper means is a thin, sheetlike member of resilient metal.

Claim 18

The apparatus of claim 12, together with a support means, means supporting said knife means for pivotal movement relative to said support means, and means so supporting said scaper means from said support means that the scraper means is stationary with respect to the axis about which the knife means pivots.

Claim 19

Apparatus for filtering suspensions comprising a hollow, cylindrical, rotary filter continuously rotatable about a horizontal axis while the pressure within said filter is maintained at a level below the pressure exteriorly of the filter; means for effecting the application of the suspension to be filtered to the exterior of said filter and for interrupting the application of the suspension thereto; and means for removing material of reduced liquid content from the exterior of the filter which comprises knife means which has a cutting edge and which is movable between an operative position in which the knife means is engageable with the material of the filter and an inoperative position in which the knife means is isolated from said layer and a scraper means engageable with said knife means as the latter is moved from the operative to the inoperative position thereof to displace from said knife means material removed from the rotary filter and adhered to said knife means, said scraper means also being engageable with the cutting edge of said knife means as said knife means is moved towards said inoperative position to thereby hone said cutting edge and keep it sharp.

Claim 20

Apparatus for filtering suspensions comprising a hollow, cylindrical, rotary filter continuously rotatable about a horizontal axis while the pressure within said filter is maintained at a level below the pressure exteriorly of the filter; means for effecting the application of the suspension to be filtered to the exterior of said filter and for interrupting the application of the suspension thereto; and means for removing material of reduced liquid content from the exterior of the filter which comprises knife means which has a cutting edge and which is movable between an operative position in which the knife means is engageable with the material of the filter and an inoperative position in which the knife means is isolated from said layer and a scraper means engageable with said knife means as the latter is moved from the operative to the inoperative position thereof to displace from said knife means material removed from the rotary filter and adhered to said knife means, said scraper means also being engageable with the cutting edge of said knife means as said knife means is moved towards said inoperative position to thereby hone said cutting edge and keep it sharp.