Patent Publication Number: US-9410286-B2

Title: Screening apparatus, rotor, wing package and method for manufacture

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/SE2013/051402 filed Nov. 27, 2013, published in English, which claims priority from Swedish Application No. 1251345-3 filed Nov. 28, 2012, all of which are hereby incorporated herein by reference. The invention relates to a screening apparatus according to the preamble of claim  1 , to a rotor and wing package for said screening apparatus and to a method for manufacture of said screening apparatus. 
     FIELD OF THE INVENTION 
     The present invention relates to a screening apparatus. More particularly, the present invention relates to a rotor and wing package for said screening apparatus and to a method for manufacture of said screening apparatus. 
     BACKGROUND OF THE INVENTION 
     Screening in papermaking means separation of foreign or different particles from a pulp suspension and may be done in different process steps in a fiber line. 
     Pulp from cooking inevitably contains unwanted solid material. Some of the chips may not have cooked properly, and some of the fibrous material may not be completely in the form of individual fibers. Defects in wood may show up as non-fibrous solids. Contaminants other than wood may also enter cooking with chips. The purpose of screening is to remove these impurities from the main pulp stream for reject treatment as efficiently as possible and wash off the good fibers, return these to the main pulp stream and prepare the reject for treatment. 
     A screening apparatus, see e.g. EP0 444 051, may comprise a screen housing enclosing a cylindrical barrier, called a screen member, having apertures in the form of e.g. holes or slits for the actual screening. The screening apparatus may further comprise an inlet for the pulp suspension leading into the screen member, an accept outlet for accept, i.e. material with small particles that has passed through the screen member from the inside and out, and a reject outlet for reject, i.e. material with large particles which has not passed the screen member. 
     To improve the screening, the screening apparatus may e.g. be provided with some sort of rotor having pulsations members, e.g. blades or protrusions. Said rotor rotates inside the screen member or else the screen member may be rotating. Further, the screen member may be provided with different variants of protrusions on its inner surface. 
     In the prior art section of EP 205 623 there is shown an open solution with wings attached to a “spider” and a reinforcement ring. The loose structure is very unstable and not sufficiently rigid to withstand the forces especially since the wings are attached with screws or bolts. A similar loose, unstable structure is shown in U.S. Pat. No. 4,328,096. 
     In EP 444 051 and EP 868 564 the rotor is designed as a cylindrical rotor body having arms with pulsation generating members, also called blades or wings, which are attached on the mantle area of the rotor body. They have complicated manufacture, since a complicated fixture is needed in order to position the wings radially and circumferentially. Several complicated fixtures are needed to be able to handle different screening apparatus sizes as well. 
     It is also complicated to change the wings, when they are worn or if you want to change the wing design e.g. in order to optimize the energy consumption. In order to get sufficient precision, the wings are preferably cast, which may cause strength problems. Further, cast wings may be warped and have to be aligned. Cracks may occur in cast wings. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, these and other problems have now been solved by the invention of a screening apparatus for screening a pulp suspension comprising a casing, a screening member disposed within the casing, a rotor disposed for rotation relative to the screening member, whereby a screening chamber is formed between the rotor and the screening member, a pulp inlet for providing the pulp to the rotor, an accept outlet for accepting pulp passing through the screening member, and a reject outlet for rejected pulp not passing through the screening member, the rotor including a rotor body and detachable pulsation package comprising at least one attachment ring attached to the rotor body, at least one support ring attached to or supported by the rotor body, and at least one pulsation member attached to the at least one attachment ring and at the least one support ring. Preferably, the screening member is cylindrical In one embodiment, the rotor body includes a pair of end surfaces and the attachment ring is attached to one of the end surfaces of the rotor body. Preferably, at least one attachment ring has a circular profile including an inner portion and an outer portion, and the inner portion of the at least one attachment ring is attached to the rotor body. 
     In accordance with another embodiment of the screening apparatus of the present invention, the at least one pulsation member includes a first end and a second end, wherein the first end of the at least one pulsation member is attached to the at least one attachment ring and the second end of the at least one pulsation member is attached to the at least one support ring. Preferably, one of the first and second ends of the at least one pulsation member extends a distance of at less than about 200 mm outside of the attachment of the at least one pulsation member to the at least one attachment ring or the at least one support ring. 
     In accordance with another embodiment of the screening apparatus of the present invention, the apparatus includes at least two pulsation members, and the at least one attachment ring includes an outer periphery including cut-out portions between the attachments of the at least two pulsation members to the at least one attachment ring, in order to improve the pulp flow therein. 
     In one embodiment, the at least one support ring includes an outer periphery including cut-out portions between the attachment of the at least two pulsation members to the at least one support ring, in order to improve the pulp flow therein. In one embodiment, the pulsation member comprises a bent plate. In another embodiment, the pulsation member comprises a cast profile. 
     In accordance with another embodiment of the screening apparatus of the present invention, the apparatus includes a dilution water outlet proximate to the rotor body, the rotor body also including a wear ring proximate to the dilution water outlet. 
     In accordance with the present invention, a rotor has also been invented for use in a screening apparatus for screening pulp suspensions, the screening apparatus comprising a casing, a screening member disposed within the casing, a rotor disposed for rotation relative to the screening member, whereby a screening chamber is formed between the rotor and the screening member, a pulp inlet for providing the pulp to the rotor, an accept outlet for accepting pulp passing through the screening member, and a reject outlet for rejected pulp not passing through the screening member, the rotor including a detachable pulsation package containing at least one attachment ring attached to the rotor body, at least one support ring attached to or supported by the rotor body, and at least one pulsation member attached to the at least one attachment ring and the at least one support ring. In a preferred embodiment, the rotor body includes a pair of end surfaces and the attachment ring is attached to one of the end surfaces of the rotor body. 
     In accordance with the present invention, a pulsation member package has also been invented for a screening apparatus for screening pulp suspensions, the screening apparatus comprising a casing, a screening member disposed within the casing, a rotor disposed for rotation relative to the screening member, wherein a screening chamber is formed between the rotor and the screening member, a pulp inlet for providing the pulp to the rotor, an accept outlet for accepting the pulp passing through the screening member, a reject outlet for rejected pulp not passing through the screening member, and a detachable pulsation member package arranged for attachment to the rotor body, the detachable pulsation member package comprising at least one attachment ring attached to the rotor body, at least one support ring attached to or supported by the rotor body, and at least one pulsation member attached to the at least one attachment ring and the at least one support ring. In a preferred embodiment, the rotor body includes an end surface, and the attachment ring is arranged to be attached to the end surface of the rotor body. 
     In accordance with the present invention, a method has also been devised for the manufacture of a rotor for screening apparatus comprising providing at least one attachment ring, at least one support ring, and at least one pulsation member; providing a rotor body having an end surface; aligning at least one attachment ring and the at least one support ring along the rotor body; attaching the at least one pulsation member to the at least one attachment ring and to the at least one support ring; and attaching the at least one attachment ring to the rotor body and attaching or supporting at least one support ring to the rotor body. In a preferred embodiment the method includes attaching the at least one pulsation member to the at least one attachment ring and the at least one support ring on the end surface of the rotor body. 
     In accordance with the present invention, a method has also been devised for the manufacture of a pulsation member package for screening apparatus comprising providing at least one attachment ring, at least one support ring and at least one pulsation member, whereby the at least one attachment ring is arranged to be attached to a rotor body; providing a fixture; aligning at least one attachment ring and the at least one support ring along the fixture; and attaching the at least one pulsation member to the at least one attachment ring and at least one support ring to the fixture. 
     One advantage of the present invention is that manufacture is made simpler. Further, when the pulsation members become worn, the pulsation member package is easily replaced as a spare part, without any need for replacing the whole rotor. Thus, the rotor body may be reused. 
     Another advantage of the present invention is higher flexibility. One possibility is to have the rotor body as a standardized part, which is the same for all or many different types of screening apparatuses. The rotor body is then only used with the pulsation member package that is appropriate for the screening apparatus in question. This makes manufacture cheaper and simpler. 
     Further, for example, if one wishes to test different pulsation member configurations for optimization of e.g. energy consumption, production or screening result, the pulsation member package may be easily exchanged and tested also by the customer himself. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention, together with further objects and advantages thereof, may best be understood by reference to the following member description and appended drawings, in which: 
         FIG. 1 a    is a side elevational partially cross-sectional view of a screening apparatus according to one embodiment of the present invention; 
         FIG. 1 b    is a partial side sectional view of the portion A of the screening apparatus shown in Figure al; 
         FIG. 2 a    is a side elevational view of a rotor with a pulsation member package according to another embodiment of the present invention; 
         FIG. 2 b    is a side, elevational view of a rotor in accordance with the embodiment of the present invention shown in  FIG. 2   a;    
         FIG. 2 c    is a side elevational view of a pulsation member package for use in the embodiment of the present invention shown in  FIG. 2   a;    
         FIG. 2 d    is a side elevational cross-sectional view of the rotor and pulsation member package shown in  FIG. 2   a;    
         FIG. 2 e    is a top elevational view of the rotor and pulsation member package shown in  FIG. 2   a;    
         FIG. 2 f    is a partial side cross-sectional view of the portion of the rotor and pulsation package shown in  FIG. 2 d    designated by section B; 
         FIG. 3 a    is a top side elevational view of a rotor with a pulsation member package in accordance with another embodiment of the present invention; 
         FIG. 3 b    is a side cross-sectional view of the rotor with pulsation member package shown in  FIG. 3 a   ; and 
         FIG. 4  is a schematic flow chart illustrating a manufacturing process according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the drawings, similar or corresponding elements are denoted by the same reference numbers. 
     In  FIG. 1 a - b    is shown a screening apparatus. In this example the screening apparatus is a single screening apparatus, but the invention may of course be used in any screening apparatus—coarse or fine—having one or more screening members. 
     The screening apparatus in  FIG. 1 a - b    comprises an air-tight casing  1  with an inlet  2  for pulp suspension, an accept outlet  3 , a reject outlet  4  and a dilution water inlet  25 . In the casing  1  a cylindrical screening member  5  is arranged, preferably with the axis of symmetry being vertical. 
     Within the screening member  5  a rotor  8  is located, which rotor  8  comprises a cylindrical or conical rotor body  10  and a detachable pulsation member package  11 . The rotor  8  is concentric with the screening member  5 , so that a screening chamber  9  is formed between the rotor  8  and the screening member  5 . A not shown motor drives the rotor  8 . 
     It is to be understood that the rotor embodiments described in the following description is not restricted to the screening apparatus shown in  FIG. 1 a - b   , but may be used in any kind of screening apparatus for coarse or fine screening, for screening from inside and out or for screening outside and in, etc. 
     In  FIG. 2 a - f    another embodiment of the rotor  8  is shown in more detail. In  FIG. 2 b    the rotor body  10  is shown without the pulsation member package  11 . In  FIG. 2 c    the pulsation member package  11  is shown without the rotor body  10 . 
     The rotor body  10  preferably has a cylindrical, conical or similar stable shape. The pulsation member package in  FIG. 2 a - c    comprises an attachment ring  12 , a first support ring  15 , a second support ring  16  and seven pulsation generating members  17 , such as wings. The attachment ring  12  in  FIG. 2 a - c    is preferably located in one end of the pulsation member package  11 , while the first support ring  15  is located in the other end of the pulsation member package  11  and the second support ring  16  is located in between the attachment ring  12  and the first support ring  15 . The pulsation members  17  are attached to the attachment ring  12 , the first support ring  15  and the second support ring  16 . 
     The attachment ring  12  is preferably attached to an end surface  13  of the rotor body  10 . It is of course possible to instead attach the attachment ring  12  on a mantle surface  14  of the rotor body  10  and then e.g. have the attachment ring  12  between the first support ring  15  and the second support ring  16 . However, an attachment on the end surface  13  will be more stable and less influenced by the passing pulp. The attachment is especially stable if the attachment is made all around the attachment ring  12 , especially if the inner part  20  of the attachment ring  12  is provided with a circular profile, and said inner part  20  is attached to the rotor body  10 . 
     Since the pulsation member package  11  is meant as a wear part, the attachment is preferably made by screws or bolts, but welding is of course also possible. The skilled person realises that, if welding is used, the number of welding points and the weld size should be such that the weld can easily be cut off without destroying the pulsation member package  11 . Weld joints of a limited size can be used either as sole joints or together with screws or bolts. 
     It is possible to have more than one attachment ring  12 . 
     The first support ring  15  and the second support ring  16  have inner diameters  22 ,  21  that are adapted so that the support rings  15 ,  16  will be supported by the rotor body  10 . In small configurations it might be sufficient with only one support ring  15  and in large configurations more support rings might be needed for improved stability. 
     It is not necessary to attach the support rings  15 ,  16  to the rotor body  10 , as long as the support rings  15 ,  16  are supported by the rotor body  10 . It is of course possible to attach also the support rings  15 ,  16  to the rotor body  10 , but that gives a higher fit requirement and thus a higher manufacture cost. A solution with less fit requirements might be just a pin  23  attached to the rotor body  10  and a notch  24  in the support ring  15 ,  16  or vice versa, see  FIG. 2   f.    
     To improve the pulp flow through the screening apparatus and around the pulsation members  17 , the attachment ring  12  and the support rings  15 ,  16  may be provided with cut-outs  18  in their outer peripheries  19 . 
     The pulsation members  17  are preferably attached with one end  28 ,  29  to one attachment ring  12  or support ring  15  and with another end  28 ,  29  to another attachment ring  12  or support ring  15 , because that makes the most stable configuration. It is, however, possible to have pulsation members  17  having a free end  28 ,  29  that extend a bit outside the attachment ring  12  or support ring  15  as in  FIG. 1 a   . Said extension is, however, preferably not longer than 200 mm, for stability. The pulsation members  17  are preferably attached by welding, but may also be e.g. screwed or bolted. 
       FIG. 2 a - c    shows an embodiment with seven pulsation members  17 , but any number is possible. For stability, the pulsation members  17  are preferably evenly arranged around the rings  12 ,  15 ,  16 . The pulsation members  17  are simplest and cheapest made of bent plate. An alternative is to cast the pulsation members  17  in a more profiled shape. An advantage with a cast pulsation member  17  is that any shape can be achieved, e.g. like an aeroplane wing. 
       FIG. 2 a - c    shows straight pulsation members  17  that are parallel to an axis of the rotor body  10  in two dimensions. It is, however, possible also to have pulsation members  17  that are e.g. inclined in one dimension. 
     Preferably, the distance between two pulsation members  17  is the same as the width of a pulsation member  17 . The thickness of the pulsation members  17  may be e.g. 10-12 mm. 
     When the pulsation members  17  are worn, the pulsation member package  11  is easily replaced as a spare part, without any need for replacing the whole rotor  8 . Thus, the rotor body  10  may be reused. 
     A possibility is also to have the rotor body  10  as a standardized part, which is the same for all or many different types of screening apparatuses. The rotor body  10  is then just used with the pulsation member package  11  that is appropriate for the screening apparatus in question. This makes manufacture cheaper and simpler. 
     Further, if there e.g. is a wish to test different pulsation member configurations for optimization of e.g. energy consumption, production or screening result, the pulsation member package  11  may be easily exchanged and tested also by the customer himself. 
     In  FIG. 3  is shown an embodiment where the pulsation member package  11  is a cylinder  30  with an attachment ring  12  and a support ring  15  and a number of pulsation members  17 . In this embodiment the pulsation members are attached to the cylinder  30 , which cylinder  30  is attached to the attachment ring  12  and support ring  15 . This means that the pulsations members  17  are indirectly attached to the attachment ring  12  and the support ring  15 , unlike the other embodiments where the pulsation members are directly attached to the attachment ring  12  and the support ring  15 . 
     The screening apparatus may be provided with an inlet  25  for dilution water, see  FIG. 1 a - b   . If there in the other end is an outlet  26  for dilution water arranged at the rotor body  10 , then there is a risk that the rotor body  10  will wear. If e.g. the dilution water is not high enough and fibers stick at the outlet  26 , torsion and thus wear may occur. In order to keep the rotor body  10  as a part that will not wear unnecessarily, the rotor  8  may therefore be provided also with a wear ring  27  in the proximity of the dilution water outlet  26 . In this embodiment the wear ring  27  is attached on the bottom of the rotor body  10 . This means that the rotor  8  in  FIG. 1  is provided with two wear parts: a pulsation member package  11  and a wear ring  27 . The wear ring  27  may of course also be used separately as spare part. 
     When the rotor  8  is manufactured there is no need for any complicated fixtures. Either the pulsation member package  11  is applied directly on the rotor body  10  or, if the pulsation member package  11  is made as a spare part, the pulsation member package  11  is applied onto a simple fixture having the contours of a rotor body  10 . 
     First the rotor body  10  or simple fixture is made, if necessary, step  101 ,  FIG. 4 . See also any of the  FIGS. 1 a - b , 2 a - f , and 3 a   - b.    
     The attachment and support rings  12 ,  15 ,  16  are each precision cut, e.g. water cut, by cutting the contours and positions for the pulsation members  17  and the contours and positions for the cut-outs  18 , if any, between the pulsation members  17 , step  102 . If the cut is made with sufficient precision the attachment and support rings  12 ,  15 ,  16  may later serve as a fixture for the pulsation members  17 . 
     The pulsation members  17  are made by e.g. cutting and bending the pulsation members  17  from a plate or by e.g. casting the pulsation members  17  to an appropriate shape, step  103 . 
     The rotor body  10  or the simple fixture is positioned, preferably vertically, step  104 . 
     At least one attachment ring  12  and at least one support ring  15 ,  16  are aligned along the rotor body  10  or simple fixture and are attached or supported, step  105 . Supports attached to the rotor body  10  or simple fixture is preferably used for the vertical alignment. 
     At least one pulsation member  17  is attached to the at least one attachment ring  12  and the at least one support ring  15 ,  16 , step  106 . This will also enable the rotary alignment of the at least one attachment ring  12  and the at least one support ring  15 ,  16 . 
     The invention is of course not restricted to the shown embodiments, but may be varied within the scope of the claims. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.