EP0212785A1 - Apparatus for screening paper fiber stock - Google Patents
Apparatus for screening paper fiber stock Download PDFInfo
- Publication number
- EP0212785A1 EP0212785A1 EP19860303932 EP86303932A EP0212785A1 EP 0212785 A1 EP0212785 A1 EP 0212785A1 EP 19860303932 EP19860303932 EP 19860303932 EP 86303932 A EP86303932 A EP 86303932A EP 0212785 A1 EP0212785 A1 EP 0212785A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- screening
- chamber
- reject
- stock
- outlet port
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
- D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
- D21D5/02—Straining or screening the pulp
- D21D5/023—Stationary screen-drums
- D21D5/026—Stationary screen-drums with rotating cleaning foils
Definitions
- Paper mills have for many years made extensive use, for the screening of paper making stock, of screening apparatus embodying a cylindrical perforate screen member defining screening and accepts chambers on the opposite sides thereof in a closed housing and provided with a rotor member which operates in one of the chambers to keep the screen perforations open and free from solid materials tending to cling to the screen surface.
- the stock or furnish is delivered to the screening chamber adjacent one end of the screen member, and the material rejected by the screen member is collected and discharged from the opposite end of the screen member.
- the primary direction of through flow is downwardly, with the stock entering the screen chamber from above, or in some cases centrally of the screening chamber when the direction of screening is from the outside to the inside of the screen member, so that any high specific gravity reject material entrained with the stock to be screened will travel by gravity to a reject discharge chamber in the lower part of the screen, from which it is subsequently discharged.
- reject material to damage the perforate screen member as it travels through the screening chamber, especially with screens of the type wherein the screening chamber is on the inside of the perforate screen member, and wherein centrifugal force therefore will cause high specific gravity materials to travel along the screening surface.
- reject material which is becoming increasingly prevalent in waste paper stocks, is material of lower specific gravity than the paper fibers, such as pieces of plastic, especially scraps of plastic foam.
- the circulatory movement imparted to the stock in the screening chamber by whatever rotor is used will develop centrifugal force which will tend to cause such light materials to migrate toward the center of the screening and reject chambers.
- Weber U.S. Patent No. 4,166,068 discloses a different construction of screening apparatus of the general type outlined above wherein the supply flow of stock to be screened enters the apparatus by way of an inlet chamber located entirely below the screening chamber, and wherein low specific gravity reject materials, including materials of substantially the same specific gravity as accepted fiber, are collected in a reject chamber above the screening chamber, and from which they are discharged by a port located generally centrally of the top wall of the apparatus in order to ensure effective removal of light reject materials of the types discussed above.
- the high specific gravity reject materials entering through the stock inlet are retained in the inlet chamber by constructing the inlet and screening chambers so as to provide an annular space in the inlet chamber which is of greater outer diameter than the flow passage through which the stock enters the screening chamber, and producing sufficient centrifugal force in the inlet chamber to cause these high specific gravity materials, such as tramp metal and the like, to be collected in this annular space and thereby to prevent them from coming into contact with the screen member.
- Such trapped high specific gravity materials are discharged from time to time directly from this annular space by the reject outlet means, so that only materials of approximately the same specific gravity as paper fiber or a lower specific gravity are allowed to reach the screen chamber.
- the present invention is especially concerned with the provision of screening apparatus which will be especially adapted for effective and efficient screening of the reject "tailings" from a primary screening station in a system for recovering reusable paper fiber from waste paper products, such for example as a system like that in Chupka U.S. Patent No. 4,873,410.
- the tailings from the primary screening station in such a system are commonly relatively rich in light specific gravity reject materials, such particularly as pieces of plastic sheet, film and foam, but substantial quantities of good paper fiber are entrained or otherwise mixed and rejected therewith. It is for this purpose that a tailings screen is provided, and it has been common to use a vibrating screen for this purpose, but a related practical problem is that the relatively significant volume of reject materials normally leaves the tailing screen as a relatively small percentage of a correspondingly large volume of water suspension, and that water mut be eliminated before the solid reject materials can be disposed of.
- the screen of the present invention was especially developed for handling such tailings with the dual objective of recovering substantially all of the good paper making fiber and delivering the reject materials in relatively concentrated form, and preferably in substantially dewatered form for ready final disposal.
- the screen of the invention accomplishes these objectives at notably lower cost than existing screens for similar applications, particularly from the standpoint of both power and water usage.
- the screen of the invention is generally similar in construction and mode of operation to the screen disclosed in the above-noted Weber patent, but it differs therefrom in a number of significant respects. More specifically, the screen of the invention differs from the screen shown in the Weber patent in its manner and means for treating reject materials of lower specific gravity than paper fibers.
- the supply flow of stock to be screened enters the apparatus by way of an inlet chamber located below the screening chamber, and any high specific gravity materials which are present in that supply flow are trapped in the inlet chamber, in substantially the same manner as disclosed in the Weber patent.
- the solid materials in the supply flow of stock into the screening chamber consist essentially of reusable fiber and low specific gravity reject materials. Special provision may be made for minimizing the possibility of light reject materials passing through the perforations in the screen cylinder, and further for washing good fiber free from the light reject materials and then concentrating those reject materials prior to their discharge from the screen.
- Reject material which reaches this upper chamber is trapped against recirculating to the screening zone, and it is then carried further upwardly into an annular reject chamber in which it is retained while circulating about the inner wall of this chamber until the quantity of reject material in the chamber increases sufficiently to be carried out by way of a reject outlet port in the outer wall of the reject chamber.
- Special provision may also be made for supplying washing liquid to the washing zone of the screening chamber from above, as well as to the reject chamber, in order to promote separation of good fiber from reject material and to carry the separated fiber to perforations in the screen cylinder for passage thereto to the accepts chamber.
- Special provision may be made for dewatering the reject material discharged from the reject port to a condition in which it can be handled as a relatively dry mass while the liquid removed therefrom is handled separately. More specifically, a small screw press assembly is mounted directly on the reject port so that solid material flowing out through the reject port is trapped and then simultaneously compressed and dewatered to the condition of a relatively firm plug in which it is discharged from the downstream end of the screw press assembly. The water removed therefrom by the screw press is then readily piped away to any other desired point in the system.
- the screen embodying the invention offers special advantages for the treatment of tailings in that it accomplishes substantially complete separation of usable fiber from reject material, and especially also in that it delivers the reject material in such thoroughly dewatered form that it can be disposed of in any desired manner as in essentially dry mass. Further, by reason of its efficient and effective screening action, the screen can be equipped with a screening cylinder having screening perforations of such small size as to reject virtually all contaminant particles, even including those of specific gravities so close to those of wet paper fibers as to be incapable of separation therefrom by gravitational or centrifugal forces.
- the screening apparatus shown in Figs. 1-4 comprises a generally cylindrical vertical housing 10 mounted by a stand 11 on a base 12.
- a cylindrical perforate screen member 13 divides the central portion of the interior of the housing 10 into a screening chamber 15 and an annular accepts chamber 16 having an outlet port 17.
- the screening member 13 is provided with multiple perforations which may be of any conventional size, shape and spacing, a typical example being circular holes 0.062 inch in diameter and in such spacing as to provide an open area in the range of 10-15%.
- these perforations may comprise slots of the sizes and spacings disclosed in Seifert U.S. Patent No. 3,842,302, and the screening member may also be of the type shown in Chupka-Seifert U.S. Patent Nos. 4,155,841 or 4,383,918.
- the inlet chamber 20 Below the screening member 13 is the inlet chamber 20, to which stock to be screened is supplied by way of a tangential inlet port 21.
- the screening member 13 is supported at its lower end by an annular flange 22 extending inwardly from the wall of housing 10 and cooperating therewith to define an annular space 25 which extends around the outside of the inlet chamber 20 and has an inner diameter equal to that of the lower end of screening member 13.
- a discharge port 26 from space 25 acts as a collection boot for trapping such reject material and may be provided with a suitable valve for periodic or intermittent dumping as disclosed in the Weber patent.
- a rotor assembly indicated generally at 30 and including a hub 31 secured to the upper end of a drive shaft 32 supported by a suitably sealed bearing assembly 33 on a bracket 34 mounted within the stand 11.
- the rotor assembly is shown as comprising four vanes 35 mounted by arms 36 on the hub 31.
- the rotor hub 31 is a cylindrical body of substantial diameter in order to reduce the radial dimension of the screening chamber 15 in accordance with principles of the invention as described hereinafter.
- the rotor hub 31 is provided adjacent its upper end with a radially extending flat disk baffle 40 having a circular periphery, except where it is cut out to accommodate the vanes 35.
- the baffle 40 constitutes a partition separating the screening chamber 15 into a lower zone 41 and an upper zone 42, and the outer diameter of the baffle 40 is slightly smaller than the inner diameter of the screening member 13, e.g. one inch, to provide a correspondingly restricted annular passage 44 connecting these zones 41 and 42.
- baffle 45 of inverted frustoconical shape is also mounted as shown on the rotor hub 31 and secured to the underside of the baffle 40.
- This frustoconical baffle 44 further restricts the size of the lower screening chamber zone 41, and it also serves to direct the upward flow of stock from the inlet chamber 20 radially outward towards the annular passage 44, as further explained hereinafter.
- the uppermost section of the housing 10 encloses a chamber 50 which corresponds to the reject chamber for low specific gravity materials in the screening apparatus of the Weber patent, but in accordance with the present invention, special features are incorporated in this chamber to minimize the possibility of recirculation of any stock from the upper end of the screening chamber to the lower end thereof.
- These provisions have the dual objective of reducing the possibility of inclusion of such reject materials in the accepted stock, and also of accumulating, and thus concentrating, such reject material in the upper part of the housing for ultimate discharge in substantially dewatered condition as described hereinafter.
- An annular disk baffle 51 is positioned in the chamber 50 to overlie the screening chamber 15.
- the inner diameter of the baffle 51 is approximately equal to the inner diameter of the screening chamber 15, and a cylindrical baffle 52 depends from the inner periphery of the baffle 51 into the upper end of the screening chamber 15, and preferably into closely spaced relation with the partition baffle 40.
- the cylindrical baffle 52 thus forms an inner wall for the upper screening chamber zone 42, and it also cooperates with the horizontal baffle 51 to form a restricted annular chamber 55 for receiving stock which flows upwardly from the screening chamber carrying low specific gravity reject materials.
- An outlet port 56 for this stock leads tangentially from the chamber 55.
- the stock to be screened is supplied to the inlet chamber 20 through inlet port 21 at sufficient velocity, e.g. 400-600 ft. min., to develop enough centrifugal force within the inlet chamber to cause any high specific gravity contaminant materials to travel directly to and around the peripheral wall of chamber 20.
- These heavy reject materials will accordingly be concentrated in the annular space 25 and delivered from there by centrifugal force into the reject port 26. None of this heavy reject material will therefore be able to reach the screening chamber 15 through the flow passage thereto defined by the inner periphery of the flange 22 which supports the lower end of the screening member 13.
- the action of the rotor assembly 30 will have a number of effects on the solid material initially mixed with the feed stock. It will initially create additional centrifugal force causing the good fiber, which is slightly heavier than water, to travel to and through the screening member 13.
- this screening apparatus is further increased by supplying washing liquid to the reject chamber 55 in order to enhance the separation in that chamber of good fiber from reject particles.
- the upper chamber 50 is provided with a water inlet 57 in its top wall 58, and water is supplied through that inlet at sufficient pressure to cause it to enter the screening chamber zone 42 through the clearance between the lower end of the cylindrical baffle 52 and the rotor hub and partition baffle 40 thereon.
- This flow of washing liquid into the chamber 55 has the dual effect of preventing light reject particles from escaping into the chamber 50, and also of washing good fiber free from the light reject material in zone 42.
- the most important operational feature is that the light reject materials entrained in the feed flow of stock are forced very quickly to and through the annular passage 44 into the upper screening chamber zone 42. Further, the light reject materials which reach the zone 42 are retained therein and in the reject chamber 55 and are thus prevented from recirculating within the housing 10 back to the lower end of the screening chamber 15 and its lower zone 41.
- a T-fitting 60 has its central port 61 directly mounted on the reject discharge port 56, and a casing 62 is mounted on one of the other two ports of this fitting.
- a screw press comprising a compaction screw 65 extending through the major part of the fitting 60 and also in the casing 62, and a perforated cylinder 66 mounted within the casing 62.
- the compacted reject material collects at the outer end of the casing 62, which is normally closed by a cover plate 80 that includes a supporting arm 81 having a pivotal mounting 82 on the casing 62 about which cover plate 80 can swing into and out of closing relation with the open end of casing 62.
- the cover plate 80 is normally biased to closed position by means such as a fluid pressure cylinder 83 having its closed end pivotally mounted at 84 on the other end of the casing 62 and having its piston 85 pivotally connected at 86 to the cover plate arm 81.
- the cylinder 83 is supplied with operating fluid at a predetermined pressure in the direction to hold the cover plate 80 closed. Then as the solid material accumulates between the inner surface of cover plate 80 and the screw 65, it will overcome this pressure, force the cover plate open, and discharge as relatively dry compacted solid material into a suitable receptacle, not shown.
- the degree of dryness can readily be controlled by regulation of the operating pressure in cylinder 83, in that extrusion of the reject material can occur only after it has been sufficiently compacted, and correspondingly dewatered, to force cover plate 80 open against that pressure.
- a cylindrical perforate screen member 113 divides the central portion of the interior of the housing 110 into a screening chamber 115 and an annular accepts chamber 116 having an outlet port 117.
- the stock enters the lower end of the screening chamber 115 from an inlet chamber 120 wherein high specific gravity reject material is trapped for separate removal as previously described
- the rotor assembly 130 includes a hub 131 secured on the upper end of the drive shaft 132.
- This rotor assembly is shown as incorporating two oppositely disposed vanes 135 which are mounted on the hub 131 by arms 136 extending from the lower portion of the hub, and by the flat disk baffle 140, which has the same function as the baffle 40 in separating the screening chamber into a lower zone 141 and an upper zone 142 connected by an annular passage 144.
- the inverted frustoconical baffle 145 functions in the same manner as described for baffle 45, and it also serves as a brace for the flat disk baffle 140.
- Both of baffles 140 and 145 are shown as provided with a plurality of evenly distributed holes 146 and 147 which contribute to the washing operation of this screen as described hereinafter.
- annular top plate 151 corresponds to the annular baffle 51 in Fig. 2 and supports a cylindrical casing 153 which cooperates with a cylindrical baffle 152 to define an annular reject chamber 155.
- the outlet port 156 from chamber 155 is shown as leading radially from the casing 153 but could of course be located to extend tangentially therefrom if desired.
- the interior of the cylindrical baffle 152 is connected with a supply pipe 157 for washing water which extends upwardly from the top cover 158 for casing 153.
- the cylindrical baffle 152 extends at its lower end into relatively closely spaced relation with the upper surface of disk baffle 140 to provide a cylindrical slot therebetween through which washing liquid can flow into the upper zone 142 of the screening chamber.
- the cylindrical baffle 152 is provided with multiple discharge holes 159 for washing liquid which are spaced around its periphery in that portion of the baffle below the level of the cover plate 151. Above that level, however, there are similar holes 159 only in the portion of the wall of cylindrical baffle 152 facing away from the reject outlet 156, and there are no such holes through which washing liquid can be discharged directly toward the reject outlet port 156.
- reject material carried out in the screen of the invention is not limited to the separation of good fiber from lower specific gravity materials.
- a common constituent in the tailings from the primary screening station of a waste paper system has been found to comprise small bits of wet strength paper which are of essentially the same specific gravity as good paper fibers.
- reject pieces which are too large for passage through the perforations in the screening cylinder 113 are caused to travel upwardly within the screening chamber, and after they are rejected by the perforations in the screen member 113, the upward pressure flow will ultimately carry them into the reject chamber 155 from which they reach its outlet 156.
Abstract
Description
- Paper mills have for many years made extensive use, for the screening of paper making stock, of screening apparatus embodying a cylindrical perforate screen member defining screening and accepts chambers on the opposite sides thereof in a closed housing and provided with a rotor member which operates in one of the chambers to keep the screen perforations open and free from solid materials tending to cling to the screen surface. In operation, the stock or furnish is delivered to the screening chamber adjacent one end of the screen member, and the material rejected by the screen member is collected and discharged from the opposite end of the screen member.
- The Applicants have manufactured and sold many such screens, originally in accordance with Staege U.S. Patent No. 2,347,716, and subsequently in accordance with Martindale U.S. Patent No. 2,835,173, the latter construction being characterized by a rotor comprising bars or vanes of air-foil section in closely spaced but non-contacting relation with the surface of the screen member. Similar screens have been marketed for some years, in competition with those of the Applicants, in accordance with other patents, such as Cannon et al U.S. Patent No. 2,975,899, Lamort U.S. patent No. 3,617,008 and Holz U.S. Patent No. 3,581,983.
- The art has also experimented widely with detailed variations in screens of the above type, including variations in the size, spacing and configuration of the perforations in the screen member and also in the vane shape and in other forms of rotor. For example, such screens have been offered in recent years wherein the rotor is a drum-like member provided with multiple bumps or other offset portions over its surface. Typical such constructions are shown in Clarke-Pounder U.S. patent No. 3,363,759 and Bolton et al U.S. Patent No. 3,726,401.
- In all of the vertically oriented commercial screens of the type outlined above, the primary direction of through flow is downwardly, with the stock entering the screen chamber from above, or in some cases centrally of the screening chamber when the direction of screening is from the outside to the inside of the screen member, so that any high specific gravity reject material entrained with the stock to be screened will travel by gravity to a reject discharge chamber in the lower part of the screen, from which it is subsequently discharged. Necessarily, therefore, there is substantial opportunity for such reject material to damage the perforate screen member as it travels through the screening chamber, especially with screens of the type wherein the screening chamber is on the inside of the perforate screen member, and wherein centrifugal force therefore will cause high specific gravity materials to travel along the screening surface.
- Another type of reject material, which is becoming increasingly prevalent in waste paper stocks, is material of lower specific gravity than the paper fibers, such as pieces of plastic, especially scraps of plastic foam. The circulatory movement imparted to the stock in the screening chamber by whatever rotor is used will develop centrifugal force which will tend to cause such light materials to migrate toward the center of the screening and reject chambers. However, in order to discharge these concentrated light reject materials, it is necessary for them to overcome the gravitational forces which tend to cause them to rise within the apparatus and therefore away from the reject discharge outlet.
- Weber U.S. Patent No. 4,166,068 discloses a different construction of screening apparatus of the general type outlined above wherein the supply flow of stock to be screened enters the apparatus by way of an inlet chamber located entirely below the screening chamber, and wherein low specific gravity reject materials, including materials of substantially the same specific gravity as accepted fiber, are collected in a reject chamber above the screening chamber, and from which they are discharged by a port located generally centrally of the top wall of the apparatus in order to ensure effective removal of light reject materials of the types discussed above.
- In the apparatus of the Weber patent, the high specific gravity reject materials entering through the stock inlet are retained in the inlet chamber by constructing the inlet and screening chambers so as to provide an annular space in the inlet chamber which is of greater outer diameter than the flow passage through which the stock enters the screening chamber, and producing sufficient centrifugal force in the inlet chamber to cause these high specific gravity materials, such as tramp metal and the like, to be collected in this annular space and thereby to prevent them from coming into contact with the screen member. Such trapped high specific gravity materials are discharged from time to time directly from this annular space by the reject outlet means, so that only materials of approximately the same specific gravity as paper fiber or a lower specific gravity are allowed to reach the screen chamber.
- The present invention is especially concerned with the provision of screening apparatus which will be especially adapted for effective and efficient screening of the reject "tailings" from a primary screening station in a system for recovering reusable paper fiber from waste paper products, such for example as a system like that in Chupka U.S. Patent No. 4,873,410.
- The tailings from the primary screening station in such a system are commonly relatively rich in light specific gravity reject materials, such particularly as pieces of plastic sheet, film and foam, but substantial quantities of good paper fiber are entrained or otherwise mixed and rejected therewith. It is for this purpose that a tailings screen is provided, and it has been common to use a vibrating screen for this purpose, but a related practical problem is that the relatively significant volume of reject materials normally leaves the tailing screen as a relatively small percentage of a correspondingly large volume of water suspension, and that water mut be eliminated before the solid reject materials can be disposed of.
- The screen of the present invention was especially developed for handling such tailings with the dual objective of recovering substantially all of the good paper making fiber and delivering the reject materials in relatively concentrated form, and preferably in substantially dewatered form for ready final disposal. In addition, the screen of the invention accomplishes these objectives at notably lower cost than existing screens for similar applications, particularly from the standpoint of both power and water usage.
- The screen of the invention is generally similar in construction and mode of operation to the screen disclosed in the above-noted Weber patent, but it differs therefrom in a number of significant respects. More specifically, the screen of the invention differs from the screen shown in the Weber patent in its manner and means for treating reject materials of lower specific gravity than paper fibers.
- The supply flow of stock to be screened enters the apparatus by way of an inlet chamber located below the screening chamber, and any high specific gravity materials which are present in that supply flow are trapped in the inlet chamber, in substantially the same manner as disclosed in the Weber patent. Thus the solid materials in the supply flow of stock into the screening chamber consist essentially of reusable fiber and low specific gravity reject materials. Special provision may be made for minimizing the possibility of light reject materials passing through the perforations in the screen cylinder, and further for washing good fiber free from the light reject materials and then concentrating those reject materials prior to their discharge from the screen.
- It is important to this objective that provision be made for preventing light reject materials which have passed through the screening chamber from recirculating back to its inlet end. This result may be accomplished by a baffle arrangement which in effect separates the screening chamber into a lower zone from which most of the good fiber is accepted, and an upper zone wherein the light reject material is subjected to a washing action to separate the good fiber therefrom and to carry it through the screen cylinder to the accepts chamber.
- Reject material which reaches this upper chamber is trapped against recirculating to the screening zone, and it is then carried further upwardly into an annular reject chamber in which it is retained while circulating about the inner wall of this chamber until the quantity of reject material in the chamber increases sufficiently to be carried out by way of a reject outlet port in the outer wall of the reject chamber. Special provision may also be made for supplying washing liquid to the washing zone of the screening chamber from above, as well as to the reject chamber, in order to promote separation of good fiber from reject material and to carry the separated fiber to perforations in the screen cylinder for passage thereto to the accepts chamber.
- Special provision may be made for dewatering the reject material discharged from the reject port to a condition in which it can be handled as a relatively dry mass while the liquid removed therefrom is handled separately. More specifically, a small screw press assembly is mounted directly on the reject port so that solid material flowing out through the reject port is trapped and then simultaneously compressed and dewatered to the condition of a relatively firm plug in which it is discharged from the downstream end of the screw press assembly. The water removed therefrom by the screw press is then readily piped away to any other desired point in the system.
- In summary, the screen embodying the invention offers special advantages for the treatment of tailings in that it accomplishes substantially complete separation of usable fiber from reject material, and especially also in that it delivers the reject material in such thoroughly dewatered form that it can be disposed of in any desired manner as in essentially dry mass. Further, by reason of its efficient and effective screening action, the screen can be equipped with a screening cylinder having screening perforations of such small size as to reject virtually all contaminant particles, even including those of specific gravities so close to those of wet paper fibers as to be incapable of separation therefrom by gravitational or centrifugal forces.
- In order that the invention may be more readily understood, reference will now be made to the accompanying drawings, in which:
- Fig. 1 is a perspective view illustrating one form of screening apparatus in accordance with the invention;
- Fig. 2 is a somewhat diagrammatic view, generally in vertical section, showing the operation and internal construction of the screening apparatus of Fig. 1;
- Fig. 3 is a section generally on the line 3--3 of Fig. 1;
- Fig. 4 is a fragmentary section similar to Fig. 2 and showing a modified form of screening apparatus in accordance with the invention; and
- Fig. 5 is a fragmentary section on the line 5--5 of Fig. 4.
- The screening apparatus shown in Figs. 1-4 comprises a generally cylindrical
vertical housing 10 mounted by a stand 11 on abase 12. A cylindricalperforate screen member 13 divides the central portion of the interior of thehousing 10 into ascreening chamber 15 and anannular accepts chamber 16 having anoutlet port 17. Thescreening member 13 is provided with multiple perforations which may be of any conventional size, shape and spacing, a typical example being circular holes 0.062 inch in diameter and in such spacing as to provide an open area in the range of 10-15%. Alternatively, these perforations may comprise slots of the sizes and spacings disclosed in Seifert U.S. Patent No. 3,842,302, and the screening member may also be of the type shown in Chupka-Seifert U.S. Patent Nos. 4,155,841 or 4,383,918. - Below the
screening member 13 is theinlet chamber 20, to which stock to be screened is supplied by way of atangential inlet port 21. Thescreening member 13 is supported at its lower end by anannular flange 22 extending inwardly from the wall ofhousing 10 and cooperating therewith to define anannular space 25 which extends around the outside of theinlet chamber 20 and has an inner diameter equal to that of the lower end ofscreening member 13. - The tangential entry of the stock through the
inlet port 21 creates centrifugal force effective to carry high specific gravity material, e.g. tramp metal, into thisspace 25 where it is retained by theflange 22 against entry to thescreening chamber 15. Adischarge port 26 fromspace 25 acts as a collection boot for trapping such reject material and may be provided with a suitable valve for periodic or intermittent dumping as disclosed in the Weber patent. - Within the
screening chamber 15 is a rotor assembly indicated generally at 30 and including ahub 31 secured to the upper end of adrive shaft 32 supported by a suitably sealedbearing assembly 33 on abracket 34 mounted within the stand 11. The rotor assembly is shown as comprising fourvanes 35 mounted byarms 36 on thehub 31. Preferably, therotor hub 31 is a cylindrical body of substantial diameter in order to reduce the radial dimension of thescreening chamber 15 in accordance with principles of the invention as described hereinafter. - The
rotor hub 31 is provided adjacent its upper end with a radially extendingflat disk baffle 40 having a circular periphery, except where it is cut out to accommodate thevanes 35. Thebaffle 40 constitutes a partition separating thescreening chamber 15 into alower zone 41 and anupper zone 42, and the outer diameter of thebaffle 40 is slightly smaller than the inner diameter of thescreening member 13, e.g. one inch, to provide a correspondingly restrictedannular passage 44 connecting thesezones - An
additional baffle 45 of inverted frustoconical shape is also mounted as shown on therotor hub 31 and secured to the underside of thebaffle 40. Thisfrustoconical baffle 44 further restricts the size of the lowerscreening chamber zone 41, and it also serves to direct the upward flow of stock from theinlet chamber 20 radially outward towards theannular passage 44, as further explained hereinafter. - The uppermost section of the
housing 10 encloses achamber 50 which corresponds to the reject chamber for low specific gravity materials in the screening apparatus of the Weber patent, but in accordance with the present invention, special features are incorporated in this chamber to minimize the possibility of recirculation of any stock from the upper end of the screening chamber to the lower end thereof. These provisions have the dual objective of reducing the possibility of inclusion of such reject materials in the accepted stock, and also of accumulating, and thus concentrating, such reject material in the upper part of the housing for ultimate discharge in substantially dewatered condition as described hereinafter. - An
annular disk baffle 51 is positioned in thechamber 50 to overlie thescreening chamber 15. The inner diameter of thebaffle 51 is approximately equal to the inner diameter of thescreening chamber 15, and acylindrical baffle 52 depends from the inner periphery of thebaffle 51 into the upper end of thescreening chamber 15, and preferably into closely spaced relation with thepartition baffle 40. Thecylindrical baffle 52 thus forms an inner wall for the upperscreening chamber zone 42, and it also cooperates with thehorizontal baffle 51 to form a restrictedannular chamber 55 for receiving stock which flows upwardly from the screening chamber carrying low specific gravity reject materials. Anoutlet port 56 for this stock leads tangentially from thechamber 55. - In operation, the stock to be screened is supplied to the
inlet chamber 20 throughinlet port 21 at sufficient velocity, e.g. 400-600 ft. min., to develop enough centrifugal force within the inlet chamber to cause any high specific gravity contaminant materials to travel directly to and around the peripheral wall ofchamber 20. These heavy reject materials will accordingly be concentrated in theannular space 25 and delivered from there by centrifugal force into thereject port 26. None of this heavy reject material will therefore be able to reach thescreening chamber 15 through the flow passage thereto defined by the inner periphery of theflange 22 which supports the lower end of the screeningmember 13. - The action of the
rotor assembly 30 will have a number of effects on the solid material initially mixed with the feed stock. It will initially create additional centrifugal force causing the good fiber, which is slightly heavier than water, to travel to and through the screeningmember 13. - There will also be an initial tendency to cause rejects of specific gravities less than water to concentrate in the radially inner portion of the screening chamber. This tendency however, will be overcome by the outward funneling effect of the
frustoconical baffle 45 in combination with the pressure behind the feed stock, which will tend to channel all of the stock in thescreening chamber zone 41 radially outwardly and upwardly towards and through theannular passage 44 leading to theupper zone 42. Thus a major part of the good fiber in the entering flow will pass to the acceptschamber 16 before it reaches thepassage 44, while the solid materials retained in the stock which flows through thepassage 44 will consist primarily of low specific gravity reject materials. - As soon as this reject-carrying stock reaches the upper
screening chamber zone 42, the low specific gravity materials therein will be free to move radially inwardly toward thecylindrical baffle 52, while whatever good fiber remains inzone 42, and which is of higher specific gravity than water, will tend to separate from the reject materials for passage through the upper part of screeningmember 13 into the acceptschamber 16. The upper portions of the rotor vanes will continue to exert a circulatory force in thezone 42, causing the low specific gravity materials therein to circulate around thecylindrical baffle 52 while the liquid exiting through thedischarge port 56 will initially be relatively free of entrained particles. Very quickly, however, the concentration of light reject particles in thechamber 55 will increase to the point that some will be entrained in the exiting stock in correspondingly increasing concentrations. - The effectiveness of this screening apparatus is further increased by supplying washing liquid to the
reject chamber 55 in order to enhance the separation in that chamber of good fiber from reject particles. For this purpose, theupper chamber 50 is provided with awater inlet 57 in itstop wall 58, and water is supplied through that inlet at sufficient pressure to cause it to enter thescreening chamber zone 42 through the clearance between the lower end of thecylindrical baffle 52 and the rotor hub andpartition baffle 40 thereon. This flow of washing liquid into thechamber 55 has the dual effect of preventing light reject particles from escaping into thechamber 50, and also of washing good fiber free from the light reject material inzone 42. - In summary, it will now be seen that while the construction of the invention provides a number of significant operating and functional advantages, the most important operational feature is that the light reject materials entrained in the feed flow of stock are forced very quickly to and through the
annular passage 44 into the upperscreening chamber zone 42. Further, the light reject materials which reach thezone 42 are retained therein and in thereject chamber 55 and are thus prevented from recirculating within thehousing 10 back to the lower end of thescreening chamber 15 and itslower zone 41. - Thus light reject particles have effectively only one chance to be carried through the screening apertures in the
member 13 into the accepts chamber, namely as they approach and pass through theannular passage 44. Once they are above thebaffle partition 40, the centrifugal forces will work to keep these particles away from the screening member and cause them to be concentrated in thereject chamber 55 until they exit through therejects port 56. Both the concentration of the reject particles and the separation therefrom of good fiber are also enhanced by the provision of the invention for adding wash water to thescreening chamber zone 42. - Special provision is also made in accordance with the invention for dewatering the concentrated low specific gravity reject material before it is discharged from the screen apparatus. Referring specifically to Figs. 1 and 3, a T-fitting 60 has its
central port 61 directly mounted on thereject discharge port 56, and acasing 62 is mounted on one of the other two ports of this fitting. Mounted within the combinedfitting 60 andcasing 62 is a screw press comprising acompaction screw 65 extending through the major part of the fitting 60 and also in thecasing 62, and aperforated cylinder 66 mounted within thecasing 62. There is sufficient annular space between theparts part 66, and which collects in atrough 67 forming the bottom ofcasing 62 and having anoutlet port 68. - The end of the
screw 65 away from thescreen member 66 is mounted in agear transmission 70 secured to the other port of fitting 61 and provided with adrive motor 72. Thus solid materials reaching the fitting 60 from thereject discharge port 56 are compressed byscrew 65 in theperforated cylinder 66, and the liquid extruded therefrom flows into thetrough 67 to anoutlet port 68. From this pipe, the liquid is recirculated by suitable piping, now shown, to any other desired point in the system. - The compacted reject material collects at the outer end of the
casing 62, which is normally closed by acover plate 80 that includes a supportingarm 81 having a pivotal mounting 82 on thecasing 62 about which coverplate 80 can swing into and out of closing relation with the open end ofcasing 62. Thecover plate 80 is normally biased to closed position by means such as afluid pressure cylinder 83 having its closed end pivotally mounted at 84 on the other end of thecasing 62 and having itspiston 85 pivotally connected at 86 to thecover plate arm 81. - In operation, the
cylinder 83 is supplied with operating fluid at a predetermined pressure in the direction to hold thecover plate 80 closed. Then as the solid material accumulates between the inner surface ofcover plate 80 and thescrew 65, it will overcome this pressure, force the cover plate open, and discharge as relatively dry compacted solid material into a suitable receptacle, not shown. The degree of dryness can readily be controlled by regulation of the operating pressure incylinder 83, in that extrusion of the reject material can occur only after it has been sufficiently compacted, and correspondingly dewatered, to forcecover plate 80 open against that pressure. - In the form of the invention shown in Figs. 4 and 5, the parts corresponding to those already described in connection with Figs. 1-3 are similarly numbered 110, 111 and so forth. As in Figs. 1-3, a cylindrical
perforate screen member 113 divides the central portion of the interior of thehousing 110 into ascreening chamber 115 and an annular acceptschamber 116 having anoutlet port 117. The stock enters the lower end of thescreening chamber 115 from an inlet chamber 120 wherein high specific gravity reject material is trapped for separate removal as previously described - The
rotor assembly 130 includes ahub 131 secured on the upper end of the drive shaft 132. This rotor assembly is shown as incorporating two oppositely disposedvanes 135 which are mounted on thehub 131 byarms 136 extending from the lower portion of the hub, and by theflat disk baffle 140, which has the same function as thebaffle 40 in separating the screening chamber into alower zone 141 and anupper zone 142 connected by anannular passage 144. The invertedfrustoconical baffle 145 functions in the same manner as described forbaffle 45, and it also serves as a brace for theflat disk baffle 140. Both ofbaffles holes - In the screen of Figs. 4 and 5, the annular
top plate 151 corresponds to theannular baffle 51 in Fig. 2 and supports acylindrical casing 153 which cooperates with acylindrical baffle 152 to define an annular reject chamber 155. The outlet port 156 from chamber 155 is shown as leading radially from thecasing 153 but could of course be located to extend tangentially therefrom if desired. - At its upper end, the interior of the
cylindrical baffle 152 is connected with asupply pipe 157 for washing water which extends upwardly from thetop cover 158 forcasing 153. Thecylindrical baffle 152 extends at its lower end into relatively closely spaced relation with the upper surface ofdisk baffle 140 to provide a cylindrical slot therebetween through which washing liquid can flow into theupper zone 142 of the screening chamber. In addition, thecylindrical baffle 152 is provided with multiple discharge holes 159 for washing liquid which are spaced around its periphery in that portion of the baffle below the level of thecover plate 151. Above that level, however, there aresimilar holes 159 only in the portion of the wall ofcylindrical baffle 152 facing away from the reject outlet 156, and there are no such holes through which washing liquid can be discharged directly toward the reject outlet port 156. - The operation of this form of screen is essentially the same as already described in connection with Figs. 1-3, except for the enhanced washing effect, not only on the stock in the
upper zone 142, but also in thelower zone 141 by reason of the series ofholes cylindrical baffle 152 can pass directly into thelower zone 141 of the screening chamber. Thus the radially outward flow of washing liquid through theholes 147 in thefrustoconical baffle 145 will promote separation of good fiber from reject material in the lowerscreening chamber zone 142, while also adding a flow component to the suspension in that zone which will accelerate the movement of lower specific gravity materials to and through thepassage 144 to theupper zone 141. In that upper zone, and also in the reject collecting chamber 155, there will be enhanced washing action by the washing liquid discharged through theholes 159, which will act both on the stock which has already reached the reject chamber 155, and especially on the stock in thezone 142. - It is important to recognize that the screening, washing and collection of reject material carried out in the screen of the invention is not limited to the separation of good fiber from lower specific gravity materials. Quite to the contrary, a common constituent in the tailings from the primary screening station of a waste paper system has been found to comprise small bits of wet strength paper which are of essentially the same specific gravity as good paper fibers. Such reject pieces which are too large for passage through the perforations in the
screening cylinder 113 are caused to travel upwardly within the screening chamber, and after they are rejected by the perforations in thescreen member 113, the upward pressure flow will ultimately carry them into the reject chamber 155 from which they reach its outlet 156. - It is to be understood that for optimum operating results, the screen shown in Figs. 4 and 5 will also be provided with a dewatering screw press as described in connection with Figs. 1 and 3 and as indicated fragmentarily at 160 in Fig. 5.
- While the forms of apparatus herein described constitutes preferred embodiments of this invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.
Claims (19)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US76426385A | 1985-08-09 | 1985-08-09 | |
US764263 | 1985-08-09 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0212785A1 true EP0212785A1 (en) | 1987-03-04 |
EP0212785B1 EP0212785B1 (en) | 1991-07-31 |
Family
ID=25070186
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19860303932 Expired - Lifetime EP0212785B1 (en) | 1985-08-09 | 1986-05-23 | Apparatus for screening paper fiber stock |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0212785B1 (en) |
JP (1) | JPS6241391A (en) |
CA (1) | CA1288732C (en) |
DE (1) | DE3680605D1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5145072A (en) * | 1988-08-04 | 1992-09-08 | Oy Tampella Ab | Method for screening and treating pulp |
EP1882773A1 (en) * | 2006-07-24 | 2008-01-30 | Aikawa Iron Works Co., Ltd. | Screen apparatus |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3223239A (en) * | 1962-05-11 | 1965-12-14 | Bird Machine Co | Pressure type screening devices |
DE2413310A1 (en) * | 1974-03-20 | 1975-10-02 | Finckh Metalltuch Maschf | PRESSURE DISPLAY FOR FIBER SUSPENSIONS ASSEMBLED WITH A PIPE EXTRACTOR |
EP0036328A2 (en) * | 1980-03-17 | 1981-09-23 | The Black Clawson Company | Dual flow screening apparatus |
-
1986
- 1986-05-22 CA CA000509722A patent/CA1288732C/en not_active Expired - Fee Related
- 1986-05-23 EP EP19860303932 patent/EP0212785B1/en not_active Expired - Lifetime
- 1986-05-23 DE DE8686303932T patent/DE3680605D1/en not_active Expired - Fee Related
- 1986-07-11 JP JP16350386A patent/JPS6241391A/en active Pending
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3223239A (en) * | 1962-05-11 | 1965-12-14 | Bird Machine Co | Pressure type screening devices |
DE2413310A1 (en) * | 1974-03-20 | 1975-10-02 | Finckh Metalltuch Maschf | PRESSURE DISPLAY FOR FIBER SUSPENSIONS ASSEMBLED WITH A PIPE EXTRACTOR |
EP0036328A2 (en) * | 1980-03-17 | 1981-09-23 | The Black Clawson Company | Dual flow screening apparatus |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5145072A (en) * | 1988-08-04 | 1992-09-08 | Oy Tampella Ab | Method for screening and treating pulp |
EP1882773A1 (en) * | 2006-07-24 | 2008-01-30 | Aikawa Iron Works Co., Ltd. | Screen apparatus |
CN101113579B (en) * | 2006-07-24 | 2012-07-11 | 相川铁工株式会社 | Screen apparatus |
Also Published As
Publication number | Publication date |
---|---|
JPS6241391A (en) | 1987-02-23 |
DE3680605D1 (en) | 1991-09-05 |
EP0212785B1 (en) | 1991-07-31 |
CA1288732C (en) | 1991-09-10 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US4107033A (en) | Apparatus for cleaning fibrous suspensions of low stock consistency | |
US4356085A (en) | Rotary screening machine for pulp suspensions | |
US4267035A (en) | Pressurized rotary screening apparatus | |
US4140629A (en) | Conical screen separator | |
US4851111A (en) | Apparatus for screening paper fiber stock | |
US3448858A (en) | Centrifugal filtering apparatus | |
CA1330207C (en) | Reject screen | |
US4634521A (en) | Screening apparatus with light reject removal | |
US5358637A (en) | Apparatus for sorting and deflaking fibrous suspensions | |
EP0036329A2 (en) | Center flow screening apparatus | |
US4067800A (en) | Screening apparatus | |
FI66036C (en) | SILAPPARAT FOER MASSAUPPSLAMNING | |
US4328096A (en) | Dual flow screening apparatus | |
CA1059357A (en) | Fiberizer | |
US6109450A (en) | Apparatus for separating unwanted contaminants from fibrous slurry | |
EP0212785B1 (en) | Apparatus for screening paper fiber stock | |
US4216918A (en) | Fiberizer | |
US5143220A (en) | Apparatus for screening to remove knots from a fluid borne slurry of fibers and knots | |
CA1163236A (en) | Dual flow screening apparatus | |
US3690571A (en) | Apparatus for disintegrating and separating material in fluid suspension | |
US5221437A (en) | Screening apparatus for paper making stock | |
US3399772A (en) | Duplex pulp screen | |
US1331587A (en) | Centrifugal pulp-screen | |
US5967335A (en) | Screening device for screening a suspension | |
CN218574190U (en) | Centrifuge with sieve material function |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): DE FR GB IT |
|
17P | Request for examination filed |
Effective date: 19870827 |
|
RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: BLACK CLAWSON (FRANCE) S.A. |
|
RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: BLACK CLAWSON (FRANCE) S.A. Owner name: THE BLACK CLAWSON COMPANY |
|
17Q | First examination report despatched |
Effective date: 19890223 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR GB IT |
|
ITF | It: translation for a ep patent filed |
Owner name: JACOBACCI & PERANI S.P.A. |
|
REF | Corresponds to: |
Ref document number: 3680605 Country of ref document: DE Date of ref document: 19910905 |
|
ET | Fr: translation filed | ||
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 19920522 Year of fee payment: 7 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 19920615 Year of fee payment: 7 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 19920620 Year of fee payment: 7 |
|
26N | No opposition filed | ||
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Effective date: 19930523 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 19930523 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Effective date: 19940131 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Effective date: 19940201 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED. Effective date: 20050523 |