Abstract: The present invention relates to a screen cylinder for screening fiber suspensions of the wood processing industry. The screen cylinder comprises a rotationally symmetric screen surface located on the side of the pulp to be screened, and support rings supporting the screen surface on the opposite side; the screen surface mainly comprising grooves and screen apertures in connection with the grooves, the grooves being comprised of a side surface on the upstream side, a bottom surface, and a side surface on the downstream side, characterized in that the bottom surface of the groove rises towards the side surface of the upstream side.

Abstract: The invention realizes an improved mechanical strainer for fibrous suspensions including: a rotor; a filtering basket substantially coaxial externally to said rotor; an interspace defined between the side surfaces of said rotor and of said filtering basket; an outer casing suitable to house said filtering basket and said rotor. Inside this outer casing there are: a feeding chamber receiving the fibrous suspension to be treated, a delivery chamber of the "accepted" and a waste chamber of the "waste". The rotor is provided with a plurality of diffusing ducts developing through diverging ways according to the flow direction and being suitable to pipe the fibrous suspensions to be treated from said feeding chamber to said interspace.

Abstract: A sieve for sorting fiber suspensions, symmetrical in relation to an axis, with an inflow side for the fiber suspension to be sorted and an opposite outflow side. This sieve is useful for pressure sorting machines having a rotor that may be rotated around the axis of the sieve and that is provided with profiled elements around the inflow side of the sieve in order to generate positive and negative pressure pulses in the fiber suspension that is to be sorted. The inflow side of the sieve has grooves approximately parallel to the axis of the sieve that follow each other in the circumferential direction of the sieve. A through-channel opens into each groove. The grooves are delimited by a front and a rear side wall, seen in the direction of rotation of the profiled elements.

Abstract: A screening device is described which is adapted in particular for fiber suspensions when paper is pulped. Along the outer circumference of a rotor body, there are disposed vanes which are oriented towards a screen wall. The vane is supported by a support member made of several parts, e.g. two parts, namely of a vane carrier and a strut carrier. The strut carrier is secured to the rotor body, for example by welding. The vane carrier and the strut carrier are detachably connected with each other by a screw connection which prevents rotation therebetween. More particularly, the connection between the vane carrier and the strut carrier is of the interlocking type.

Abstract: A de-trashing unit has a rotor fabricated from steel blank. The rotor has two swept blades with blunt leading edges and relieved trailing edges. The rotor is driven to rotate over a trash screen with holes of between one-quarter and one-half inch in diameter. The blade is positioned with a clearance between the blade and the screen of between 0.005 and 0.010 inches. The relieved portions of the blades face the screen while the trailing edges of the blade are tapered between 18 and 30 degrees away from the screen surface. The blade taper creates a strong negative pressure pulse which keeps the screen clear. Holes drilled through the relieved portion of the blade allow circulation through the blade into the region of low pressure generated by the relieved portions passing over the screen. The circulation created by the holes creates microturbulence which keeps a water and paper fiber slurry fluidized.

Abstract: An apparatus and method for screening wood pulp and other fibrous fluid suspensions. The apparatus and method relate to rebuildable, modular screen cylinders for screening thick pulp slurry in pulp and paper applications. The screen sections of the modular screen cylinder of the present invention are of a nonwelded construction. A lap joint according to the present invention is provided in each screen section connecting the ends of the individual sections when the screen sections are rolled into cylindrical shape. As a result, the lap joint of the current invention provides for a nonwelded, modular screen cylinder which is less expensive to manufacture and provides for increased wear life and durability as compared to similar screen baskets previously known.

Abstract: Apparatus for screening pulp suspensions containing heavy impurities is disclosed including a casing with an inlet for the pulp suspension at the lower end of the casing, a stationary screen mounted within the casing, a rotor mounted for rotation within the stationary screen thus forming a screening zone between the rotor and the stationary screen, with the inlet disposed within the rotor, the rotor including at least one opening adjacent to its upper end for transferring the pulp into the screening zone and a chamber for the heavy impurities disposed adjacent to either the upper or lower end of the casing, the rotor including strips or grooves for moving heavy impurities from the inner surface of the rotor to the chamber.

Abstract: Apparatus for separating light impurities from a pulp suspension is disclosed. The apparatus includes a housing mounted on a fractionation device and symmetrically disposed with respect to the axis of rotation of the casing of the fractionation device, a passageway extending between the housing and the casing, and in which the top of the housing includes an outlet for the light impurities and a dilution liquid inlet for injecting dilution liquid tangentially into the housing.

Abstract: A papermaking screen apparatus is formed of a tank, cylindrical first and second screens and a stirring unit, which are disposed inside the tank. The tank holds a papermaking material, and includes a papermaking material inlet at a peripheral portion and a screened material outlet for removing a screened material from a center portion of the tank. The first screen is situated inside the tank to form an inner compartment therein connected to the outlet. The second screen is situated inside the tank and located outside the first screen to thereby form an outer chamber between an inner periphery of the tank and the second screen, and an inner chamber between the first and second screens. The second screen is at least partly overlapped with the first screen along an axial direction. The stirring unit is rotatably situated inside the tank and includes a first stirrer situated in the inner chamber adjacent to the first screen, and a second stirrer situated in the outer chamber adjacent to the second screen.

Abstract: A screen cylinder is adapted to be used with a stirring unit for screening high consistency pulp to be received in the screen cylinder. The screen cylinder includes a plurality of parallel supporting plates, each of which is formed with a plurality of transversely and spacedly arranged mounting grooves. The mounting grooves on one of the supporting plates is aligned with the mounting grooves on an adjacent one of the supporting plates. Each of a plurality of parallel elongated bars has a longitudinal constricted mounting portion to be tightly gripped by the supporting plates in the mounting grooves. Each elongated bar further has a longitudinal head portion on one end of the constricted mounting portion and a pair of longitudinal ribs which extend respectively from opposite sides of the head portion adjacent to the constricted mounting portion. The head portion has a flat end face and an opposite pair of concave side faces which extend inwardly from the end face to a respective one of the longitudinal ribs.

Abstract: A process for cleaning recycled pulp includes an upright cylindrical vessel having an upright cylindrical screen member open at its top and bottom ends and having a perforated screen wall which is centered on a vertical axis in the vessel. A plurality of upright, elongated blades are mounted for rotation on the vertical axis in close proximity to the screen wall. A pulp slurry entrained with pressurized air is introduced under pressure into an inlet in the bottom of the vessel. The rotating blades clear the screen wall while creating a rising vortex of air bubbles produced by the pressurized air for carrying ink and/or contaminant particles upwardly through the inner volume of the screen member. An "accepts" outlet at the center of the vessel draws off pulp in suspension that has been passed through the screen wall. A "rejects" outlet at the top of the vessel draws off ink and contaminant particles carried by the air bubbles in the upwardly-moving vortex.

Abstract: A pressurized screen arrangement for screening lignocellulose containing fiber material, comprising a screen housing (10) with a screen cage (11) are arranged in first and, respectively, second attachment members (17, 18) in the screen housing. Both ends of the screen cage (11) are fitted into the attachment members (17,18) with radial clearance, and an axial support (21) is provided at least at one of the attachment members (17,18).

Abstract: The differences in performance of a screening cylinder during screening of a fiber suspension (e.g. low consistency paper pulp) at the inlet end compared to the reject end is accommodated by constructing the feed side surface of the screening cylinder so that it induces greater turbulence in the vicinity of the screen cylinder surface adjacent the reject end of the screen than adjacent the inlet end. Typically this increase in turbulence is at least about 10% (preferably at least about 40%, and typically greater than 100%). The turbulence increase can be provided by a substantially smooth screening medium surface at the inlet end and a contoured screening medium surface adjacent the reject end, or by first and second contoured surfaces of different aggressiveness.

Abstract: The invention concerns a rotor with impulse elements running in the vicinity of a rotationally symmetric screen basket and with blade elements which are run radially within the impulse elements with or by the rotor, notably for use in screen graders. The invention is characterized in that a pump impeller is formed by the mutual coordination and design of the blade elements.

Abstract: A screen cylinder or plate has a screening surface and accepts surface on opposite faces, and screens pulp flowing in a flow direction to separate accepts from rejects. A number of substantially parallel macro grooves are formed in the screening surface generally transverse to the flow direction, and a number of parallel micro grooves are formed in the screening surface within each macro groove also generally transverse to the flow direction. The macro grooves induce shear stress in the reject material flowing in the flow direction to keep it in constant motion and to prevent it from forming a mat on the screening surface. The micro grooves induce micro turbulence into the pulp at the immediate area of screening openings extending from each micro groove to the accepts surface, to fluidize the pulp so that accepts readily pass through the screening openings toward the accepts surface. Each micro groove within a macro groove is located further away from the accepts surface moving in the flow direction.

Abstract: A screen module for a size reduction machine has a rigid screen having a tapered apertured wall formed in a frusto-conical shape. The rigid screen has an open wide end and a flat end. The wide end is mountable within a channel of the size reduction machine at a predetermined distance from a complementarily shaped impeller. The module has a fine screen nested within the rigid screen and against the tapered apertured wall. The fine screen has a wide end and a narrow end corresponding to the apertured wall. An adaptor disc is releasably secured within the rigid screen at the flat end. The adaptor has a tapered outer perimeter for seating against the tapered apertured wall when the adaptor disc is secured within the rigid screen, clamping the narrow end of the fine screen therebetween. A clamp ring is releasably secured at the open wide end of the rigid screen.

Abstract: An apparatus for cleaning recycled pulp includes an upright cylindrical vessel having an upright cylindrical screen member open at its top and bottom ends and having a perforated screen wall which is centered on a vertical axis in the vessel. A plurality of upright, elongated blades are mounted for rotation on the vertical axis in close proximity to the screen wall. A pulp slurry entrained with pressurized air is introduced under pressure into an inlet in the bottom of the vessel. The rotating blades clear the screen wall while creating a rising vortex of air bubbles produced by the pressurized air for carrying ink and/or contaminant particles upwardly through the inner volume of the screen member. An "accepts" outlet at the center of the vessel draws off pulp in suspension that has been passed through the screen wall. A "rejects" outlet at the top of the vessel draws off ink and contaminant particles carried by the air bubbles in the upwardly-moving vortex.

Abstract: A self-cleaning pressure filter system comprises a housing having an unfiltered liquid inlet and a filtered liquid outlet, a filter element of substantially constant cross section having an interior communicating with the unfiltered liquid inlet and an exterior communicating with the filtered liquid outlet for filtering solids from the liquid and wherein filtered out solids are left in the interior of the filtered element. A cleaning unit is simultaneously moved both axially and rotatively along the interior of the filter element and carries at least one cleaning blade movable in a spiral path along the interior face of the filter element for removing solids accumulated thereon.

Abstract: An apparatus for screening and thickening cellulose pulp keeps cleaner than conventional apparatus. Pulse members in accordance with the prior art are constructed so that when the capacity of the screening apparatus is increased, for example by using greater pressure differences or the cleanliness of the accept is increased by decreasing the size of the perforations or slots, a situation is created in which the screen cylinder tends to clog. The pulse member of the present screening apparatus subjects the screen cylinder or screen surface to a pulse cleaning action so that there is a minimal possibility to allow the pressure effect to "escape" past the area being cleaned. The higher the consistency of the fiber matting is or the worse the screen surface is clogged, the stronger the pulse cleaning of the screen surface.

Abstract: A method and apparatus are described for continuously sampling a process stream, or reservoir of aqueous cellulosic pulp and detecting oversize contaminants in the sampled stream. This serves the overall objective of estimating the level of contamination in the process stream or reservoir during a given period of production; the method may include the following stages: 1) a continuous sample stream is drawn from the process or main stream, 2) the stream is passed through a centrifugal device which divides the sampled stream according to density, 3) the stream with the higher level of contaminants from the centrifugal device is passed to a screen which isolates the contaminants, and 4) the contaminants are flushed from the screen so that they can be quantified; these measurements are used to assess the purity of the material being produced. One useful application of this invention is to assess the presence of trace amounts of plastic contaminants in the production of the cellulosic pulp.

Abstract: A replaceable screen structure for a stock screen where stock slurry for making paper is passed through a screen with the rejects going to a reject outlet and the accepts passing through openings in the screen to an accepts outlet, with the screen having projections and a rotor inducing a pulsating induced flow along the profile surface, with projections on the surface having an inclined ramp of less than about 45.degree. and a 90.degree. downstream wall and accepts flow openings between the projections positioned closer to the upstream projection than the downstream projection.

Abstract: In a sorting method for fiber suspensions, a dividing wall (3, 3') is used comprising openings via which the compenent particles in the suspension S to be sorted are classified according to their size. The beneficial transporting away of the rejected component particles is thus achieved on the inlet side (4) of the dividing wall (3,3') with the aid of flow blades (7,7'), whereas, on the outlet side (5), pressure pulses produced by clearers (6) act through the openings of the dividing wall preventing them from clogging up.

Abstract: A self-cleaning stationary basket strainer has a housing with an inlet adjacent the top and an outlet adjacent the bottom, with a stationary strainer basket contained therein spaced from the wall of the housing. A flush discharge opening and a backwash discharge opening and provided in the closed bottom of the housing. A hollow backwash conduit is provided adjacent the inner surface of the strainer basket, adapted to move about the inner periphery thereof, and has a passage in the wall thereof communicating with a chamber in the conduit. A discharge section on the hollow backwash conduit communicates with the backwash discharge opening in the housing, the backwash discharge opening sealable when not in use. A scraper blade and extension member are provided on the hollow backwash conduit forming a channel which communicates with the passage. A rotatable brush may also be used which moves about the inner periphery of the strainer basket and brushes the inner surface of the strainer basket.

Abstract: Apparatus for screening a papermaking pulp or stock suspension through a stationary cylindrical screen includes a rotating hydrofoil member which has a curved outer or camber surface portion mounted for rotation with the camber surface in a close but spaced proximity to the inside surface of the screen, in which a discrete part or segment of the body of the member is movable with respect to the body and defines a portion of the curved camber surface, so that the effective spacing between the curved surface and the adjacent inside surface of the screen may be adjusted. The hydrofoil is fabricated from sheet metal and forms an outwardly opening spanwise slot, and a sheet metal fabricated segment is received within the slot and forms a substantial continuation of the outer surface, and is adjustable by a threaded fastener which is accessible through a slot formed in the face surface of the hydrofoil.

Abstract: A screening apparatus is disclosed having at least one housing attachment element and a main housing element, each of which has a hollow cylindrical and/or truncated-cone-shaped housing outer wall. The apparatus includes at least two coaxial, predominantly rotationally symmetrical screen baskets and a rotor having pulsation elements. An accepts chamber is disposed radially outside the screen baskets and the rotor and pulsation elements are disposed radially inside the screen baskets. An inlet of the housing is disposed centrally in the area between the screen baskets and an outlet channel allowing for access in the area between the two screen baskets. The invention is characterized in that at least in the area of the screen baskets, only one main housing element and one attachment element are provided and that the first screen basket is disposed in the attachment element and the second screen basket is disposed in the main housing element.

Abstract: A device for screening pulp suspensions includes a cylindric housing (1) with inject inlet (2), reject outlet (3) and accept outlet (4) and screening members in the form of a stator (5) and a rotor (8). The stator (5) as well as the rotor (8) include a plurality of annular elements (6 and 9, respectively), which are arranged in a mutual spaced relationship. The rotor (8) is located radially outside the stator (5), so that the rotor elements (9) are located directly in front of the spaces between the stator elements (6), and the axial length of the rotor elements is greater than the spaces between the stator elements. Thereby gaps (11) are formed between the stator elements and rotor elements.

Abstract: A pressure sorter for a suspension flow includes a cylindrical housing having at least one inlet opening and at least one outlet opening with a defined pressure drop therebetween. A rotationally symmetric screen basket defining an axis is disposed within the housing. The screen basket has a plurality of openings defining a total screen perforation passage area. The axis of the screen basket is positioned offset a distance of 6 to 12% of the diameter of the screen basket. The axis of the screen basket is disposed in a plane which extends through the housing axis and is perpendicular to the housing outlet opening. A rotor and suspension sorting space are disposed centrically within the screen basket. An accepts space is disposed radially outward of the screen basket between the screen basket and the housing.

Abstract: This invention relates to a screen separator for separating metal adsorbent particles from a pulp and includes a screen separator for separating metal adsorbent particles from a pulp including an open topped and closed bottom cylindrical screen for axially vertical location, in use, in a tank containing pulp with the open top of the screen at or adjacent the full pulp surface level in the tank, an impeller which is located in the screen with its axis of rotation vertical, drive means, and a drive shaft connecting the drive means to the impeller with the impeller being adapted to drive pulp in the screen upwardly to a level above the surface level of the full pulp level in the tank when the impeller is rotated in the screen. The invention further extends to a method of separating the particles from the pulp by means of the separator and to a metal recover process which employs the separation method.

Abstract: A backwash strainer including a body, a strainer element having an inlet side contained in the body, and a space defined between the body and the strainer element. The body includes an inlet to the strainer element and an outlet from the annular space. A nozzle for directing cleaning fluid against the inlet side of the strainer element for dislodging particulate matter from the inlet side of the strainer element mounts to the body. A backwash arm for collecting the cleaning fluid and dislodging particulate matter mounts to the body. The backwash arm is positioned adjacent to and is in close proximity to the inlet side of the strainer element and the nozzle. The backwash arm has an axially extending slot defined by two spaced members having ends positioned adjacent to the nozzle. The backwash arm and the nozzle together may be moveable about a central axis relative to the strainer element.

Abstract: A rotor is disposed concentrically within a cylindrical screen. The rotor carries a plurality of blades in close proximity to the screen to produce hydrodynamic pulses opposing fluid flow to clear the screen. Each blade includes a first portion affixed to the rotor, this first portion including an inclined face and a substantially raidally extending face. A second portion of the blade is removably affixed to the radially extending face of the first portion. The removable second portion extends radially beyond the first portion. After the removable portion has become worn from extended use, it can be removed and replaced with a new second portion. In a preferred embodiment, the thickness of the second portion of the blade is equal to or greater than the diameter of holes in the screen. It is also preferred that the length of the second blade portion extending beyond the first portion be greater than the diameter of holes in the screen.

Abstract: The invention relates to a method and a screening apparatus (1) for screening pulp. In the method, the maximum length of fibres and shives flowing through holes (4a) in a screen drum (4) is adjusted by moving blades (8) with a sharp front edge close to the surface of the screen drum (4) in such a manner that the sharp edge (8a) of the front face moving closest to the drum surface strikes shives or long fibers passing through the hole (4a) and pulls them back. The rate of travel of the blades (8) is so adjusted that the pulp flows in the hole (4a) only over a distance corresponding to the predetermined fiber length during the interval between the front edge of two successive blades (8). The screening apparatus (1) comprises blades (8) moving in parallel with the surface of the screen drum (4). The front edge of the blades defines in cross-section a sharp angle, the point of the angle defined by the front edge moving closest to the surface of the screen drum (4).

Abstract: Screen cylinders, and methods of making the same for use in removing contaminant particles from papermaking stock, have a seamless cylinder body and the openings or slots therethrough are formed by directing a focused laser beam at an outer surface while focusing the beam intermediate the outer an dinner surfaces to form an opening or slot with tapered walls. Wear bars may be applied to the inside surface as a bead of weld material. The seamless cylindrical body is formed by centrifugal casting or by cold roller extrusion.

Abstract: The invention relates to a method and a device for screening and treating pulp. In the invention, the pulp is screened in a screen into an accepted fraction and a rejected fraction, the rejected fraction being treated after the screening by removing water from it. In order to reduce the energy consumption of the refining process, the rejected pulp fraction is screened by means of a means (13) rotating rapidly in a reject space (12) of a screen (1) in such a manner that the rapidly rotating means (13) effects a radial flow of the fine-grained material contained in the rejected fraction outwards through a perforated wall (14) surrounding the rotating means (13) into a space (15, 15a) from where the fine-grained material is discharged.

Abstract: The rotor of a sorter has a circumference which, in cross section perpendicular to the rotor axis of rotation, is essentially composed of circular arcs. Depending on sorter size, the number of circular arcs amounts to between two and eight. The eccentricity of the circular arcs relative to their center, based on the rotor axis of rotation, amounts to preferably between 4 and 10 mm. This makes it possible to obtain slight rotor stresses at a good sorting efficacy, preferably also with a mean substance density of more than 3% of fiber suspensions. The difference between the smallest and greatest rotor spacing e=f.sub.max -f.sub.min amounts to maximally 60 mm, preferably 20 mm.

Abstract: The pressurized screening device designed for screening fiber pulps, especially paper pulp is provided with a screenplate with perforations, cleaning members being in connection with and moving relative to the screenplate, devices for generating the relative motion between the screenplate and the cleaning members, piping firstly for introducing fiber pulp into the pressurized screening device, secondly for conducting the accepted fiber pulp into the next process stage and thirdly for discharging rejected pulp from the pressurized screening device preferably to be returned into the pressurized screening device, and guiding devices for shifting the flow direction of unscreened fiber pulp to a direction substantially perpendicular to the screenplate. The guiding devices include a combination of several compartments for guiding the flow of fiber pulp which are comprised of side walls, a back wall and baffle blades.

Abstract: A screening apparatus comprises a pair of stationary concentric screens with a plurality of foils rotating therebetween and adjacent thereto, the individual foils being radially aligned. The screening apparatus comprises a tangentially disposed slurry inlet and a diametrically and tangentially disposed heavy rejects outlet at the end of a heavy rejects trap. The light reject/accepts slurry flows into the screening zone and, after separation, is discharged at an end of the screening apparatus by way of respective light rejects and accepts outlets. The accept outlet is located axially with respect to the screen cylinders and rotating foils so the pressure pulses are virtually eliminated in the screening process. The apparatus may be constructed for vertical or horizontal rotation of the foils.

Abstract: Fiber suspension, such as paper pulp flowing to the headbox of a paper machine, is acted upon by apparatus which affects the axial direction and magnitude of the speed of the fiber suspension during screening to optimize results. A rotor cooperates with a screen cylinder, the rotor having a plurality of projections arranged along its axial length. The axial length of the rotor preferably has different axially extending circumferential zones. The projections have non-axial surfaces which act on the suspension to change the axial forces. Different shapes of projections are preferably provided in the different zones so that the axial forces vary in dependence upon the distance from the inlet to the screen casing, and the discharge outlet from the screen casing.

Abstract: In screening apparatus for paper making stock comprising a cylindrical screening member dividing the interior of a pressure housing into a supply chamber and an accepts chamber, and also comprising a rotor mounted for rotation in the supply chamber and including a plurality of vanes mounted thereon in angularly spaced relation with each other and in relatively closely spaced relation with the screening member, each of the vanes is of generally airfoil shape and is oriented with its leading edge closest to the screening member and with the surface portion thereof trailing the leading edge diverging from the screening member to create a positive pressure force along the leading edge followed by a negative pressure force between the trailing portion and the screening member.

Abstract: A method and an apparatus for treating a fiber suspension wherein the fiber suspension is fed into a treatment apparatus having treatment zones and divided into two fractions, an accept and a reject, the reject being guided from one zone behind at least one adjacent treatment zone to a separate reject treatment zone, in which the remaining accept of the suspension is discharged. The apparatus being divided into a plurality of axial zones and having a rotor and at least one screen arranged in an outer housing, and in the treatment space between the screen and the rotor, members are arranged for guiding the suspension from the different treatment zones of the treatment space to the separate reject treatment zone.

Abstract: A screen plate and method of making a screen plate for the pressure screening of papermaking stock in pressure screening apparatus includes slots which have been cut therethrough by a machining laser beam focused at the inlet side of the plate, to provide slots with nearly straight walls with minimum taper, and which are recast and have a "glassy" appearance by reason of the melting and resolidification of the immediate wall surface, to provide a low friction path for the stock. Straight, curved and inclined or slanted slots are disclosed including slots which are at a diagonal to the axis of the cylinder. Slots or openings are disclosed which are inclined to a radius line therethrough both with and against the direction of flow of the stock along the inlet surface. Wear bars are applied to the plate for coaction with the rotating foils on the screening apparatus, in the form of strips of weld material of high hardness applied directly to the plate.

Abstract: A slit screen that is simple to manufacture and excellent in working precision, which includes a screen cylinder in which at least one side of inlet corner portions of slit openings is subjected to chamfering and a cylindrical rotor rotatably disposed on the inside of the screen cylinder and having a large number of protrusions on its surface on the side thereof facing the screen cylinder. The screen cylinder can be made from a plurality of spaced-apart, identical extruded bars of suitable cross-section joined to upper and lower supports. The protrusions on the cylindrical rotor can be non-metallic elastic inserts mounted on a rotor drum.

Abstract: A screen plate and plate and method of making a screen plate for the pressure screening of papermaking stock in pressure screening apparatus includes slots which have been cut therethrough by a machining laser beam focused at the inlet side of the plate, to provide slots with nearly straight walls with minimum taper, and which are recast and have a "glassy" appearance by reason of the melting and resolidification of the immediate wall surface, to provide a low friction path for the stock. Straight, curved and inclined or slanted slots are disclosed including slots which are at a diagonal to the axis of the cylinder. Slots or openings are disclosed which are inclined to a radius line therethrough both with and against the direction of flow of the stock along the inlet surface. Wear bars are applied to the plate for coaction with the rotating foils on the screening apparatus, in the form of strips of weld material of high hardness applied directly to the plate.

Abstract: An improved screening apparatus for fiber suspensions is provided comprisingat least one stationary, generally cylindrical screen drum into which the fiber suspension is fed having a central axis and a plurality of apertures through which rejectable material from the suspension cannot pass and is retained on a reject side of the drum and through which accepted fibers from the suspension can pass to an opposite side of the drum;a generally cylindrical rotor, co-axial with the axis of the cylindrical screen drum;the rotor supporting a series of blades arranged circumferentially about the rotor and substantially aligned with the longitudinal axis of the rotor, with the lateral extent of each blade being adjacent the surface of the cylindrical screen drum; andeach blade in the series of blades having opposing ends and being inclined in the opposite direction to any adjacent blade relative to a line in the circumferential path of the blades which is parallel to the longitudinal axis of the rotor and the cylindrica

Abstract: A screen and a coaxially radially spaced rotor provide a fluid passage for the fibrous material--liquid suspension. The rotor surface has the effect of pumping or assisting a flow of dilution liquid from the reject end towards the inlet end of the fluid passage, thereby partly or wholly offsetting the natural thickening of the suspension during screening.

Abstract: A two stage rotary pulp screening device has two screens in line within a single chamber. The accepts from the second screen can be recirculated to the primary screen as an integral part of the device. The improvement comprises a second screen within the chamber, downstream and co-axial with the primary screen and having a diameter at least as large as the primary screen, the impeller extends axially in a downstream direction within the second screen and has a body shape with a circular axial cross section whose diameter increases from the outlet end of the primary screen in the downstream direction, second impeller blades radiating from a downstream portion of the impeller for the length of the second screen, and second pulp stock discharge outlet from exterior of the second screen.

Abstract: A dam is used to divide the typical single screen of a fibrous stock screening apparatus into two primary screening zones. Stock inlet and rejects outlet ports are routed to each primary screening zone. The screen is extended past the typical rotor to create an initial screening zone. One or more of the blades of the rotor may also be extended to create turbulence and/or oscillating pressures in the initial screening zone. The profile of the blades may be designed to produce a shearing action with a long moderate relief on the trailing edge to create gradual and extended negative pressure.

Abstract: In screening apparatus for paper making fiber incorporating a cylindrical screen member provided with cylindrical screening perforations, each of the perforations is characterized by a concentric frustoconical inlet end portion having a maximum diameter at the inlet surface of the screening member which is substantially greater than the portion of the perforation of minimum diameter, the maximum diameter of these inlet end portions being such that adjacent such portions closely approach or intersect each other to define multiple ridges on the surface of the inlet side of the screening member.

Abstract: A sorter having a rotationally symmetric screen including a drain space for receiving overflow material (rejects) connected axially above the screen. A screen space is provided radially outside of the screen and an accepts drain space is connected to the screen space above the screen and surrounding the drain space. The screen space receives the flow through material (accepts) and, in its upper portion, includes a gas space for dampening.

Abstract: A sorter for paper pulp suspension including a rotationally symmetrical wire cage and a rotor supporting a plurality of vanes for rotating about the interior of the cage for moving suspension through the wire cage, the vanes being non-uniformly spaced. An annular pulp chamber surrounds the screen for collecting the pulp. A suspension outlet at the bottom of the pulp chamber receives the pulp from the pulp chamber. The pulp chamber extends axially beyond the lower end of the wire cage. An annular damping chamber surrounds the lower end of the pulp chamber and flow from the pulp chamber to the pulp outlet is past the damping chamber. The damping chamber develops a pool of the suspension in it. A pressurized gas cushion above the pool of suspension in the damping chamber controls the level thereof and damps the motion of the pulp in the pulp chamber.

Abstract: In screening apparatus for paper making stock including a housing, a cylindrical perforated screen member separating the interior of the housing into a supply chamber and an accepts chamber on the inside and outside respectively of the screen member, an inlet port for supplying stock to one end of the supply chamber, an outlet port from the accepts chamber, a reject port from the supply chamber, and a rotor mounted for rotation within the screen member, the rotor is characterized by comprising a substantially circular disk which is of a thickness constituting a very minor fraction of the axial length of the screen member and has vanes mounted on its outer periphery which extend lengthwise of the screen member for rotation with the disk in the annular space between the periphery of the disk and the inner surface of the screen member.