CA1242346A - Apparatus for pulping paper - Google Patents
Apparatus for pulping paperInfo
- Publication number
- CA1242346A CA1242346A CA000448340A CA448340A CA1242346A CA 1242346 A CA1242346 A CA 1242346A CA 000448340 A CA000448340 A CA 000448340A CA 448340 A CA448340 A CA 448340A CA 1242346 A CA1242346 A CA 1242346A
- Authority
- CA
- Canada
- Prior art keywords
- rotor
- vanes
- stock
- pulping
- feed screw
- 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.)
- Expired
Links
- 238000004537 pulping Methods 0.000 title claims abstract description 39
- 238000005086 pumping Methods 0.000 claims description 17
- 239000007787 solid Substances 0.000 claims description 5
- 230000010006 flight Effects 0.000 description 15
- 230000008901 benefit Effects 0.000 description 5
- 230000033001 locomotion Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000002245 particle Substances 0.000 description 3
- 230000000630 rising effect Effects 0.000 description 3
- 241000196324 Embryophyta Species 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000037361 pathway Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 230000008093 supporting effect Effects 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21B1/00—Fibrous raw materials or their mechanical treatment
- D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
- D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
- D21B1/30—Defibrating by other means
- D21B1/34—Kneading or mixing; Pulpers
- D21B1/345—Pulpers
- D21B1/347—Rotor assemblies
Abstract
Abstract An apparatus for pulping paper making stock at high consistencies which includes a rotor (28) having a rotor body (30), a plurality of vanes (36, 38) extending generally radially outwardly therefrom and a feed screw (40) mounted centrally of the rotor body and extending upwardly therefrom along an axis of rotation of the rotor body. The feed screw includes a conical body (42) having a base (46) with a periphery adjacent root portions (48) of the rotor vanes (38) and at least one helical slight (50, 52) extending along the length of the conical body and, in one embodiment, has a tapered end (54) which is located adjacent a vane root. The rotor body (30) and feed screw (40) are mounted for rotation in a center portion of the bottom wall (14, 16) of a tub (10) for holding paper making stock such that, when the rotor (28) is rotated, the conical body (42) and helical screw (40) guide material contacting the feed screw downwardly and outwardly to contact the rotor vanes (36, 38) which impel the stock toward the side wall (12) of the tub with sufficient force to climb the wall.
Description
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APPARATUS FOR PULPING PAPER
This invention relates to apparatus for pulping paper making stock at relatively high con-sistencies, and more particularly to paper pulping apparatus in which a vaned rotor is utilized to circulate the stock within a tub.
Paper pulping apparatus typically includes a tub having a bottom wall and a cylindrical side wall extending upwardly therefrom, a vaned rotor centrally mounted on the bottom wall for rotation within the tub, and a screen or valve means located in or near the bottom wall to provide means for removal of the pulped paper stock. The rotor vanes include leading faces which are shaped and sized to contact stock near the bottom wall of the tub and propel it radially outwardly from the rotor against the side wall, which directs the stock upwardly.
The rising stock flows to the center of the tub and then downwardly toward the rotating vanes. Thus durin9 pulping operation, the stock is caused to flow in a generally clrcular pattern, and the reduc-tion in size of the individual particles of paper stock is due largely if not exclusively to the high sheer forces between particles of stock created by this flow pattern.
Many pulping devices of this construction presently in use are limited in application to paper making stock having a relatively low consistency, typically in the range of 4-7% solids content If the consistency of the stock is raised appreciably above about 7~, the density of viscosity of the stock is such that it does not easily flow downwardly between the spinning vanes of the rotor. The vanes will displace an initial quantity of pulp outwardly, but cavitation will when occur since the displaced pulp is not replaced by downwardly flowing pulp.
:
f ~4Z39~6 In order to perform a pulping process upon stock having a consistency in excess of about 10~, special rotors have been developed. For example, in the Blakly et al. U.S. Patent Application Serial No.
407,371, filed August 12,-1982 and commonly assigned, a high consistency pulping apparatus is disclosed having a rotor with a vertically oriented and axially aligned feeding screw. The rotor induces vanes in the form of circumferentially-extendin~ members with a half-crescent shape which are disposed about the periphery of a disk-shaped plate. The feeding screw is mounted in the center of the plate and includes a cylindrically-shaped body having a base which is spaced from the rotor vanes, and a helical screw flight which extends along the body and terminates at a squared end above the disk-shaped plate support-ing the vanes.
When rotated in a tub containing stock at 12-13% consistency, the feeding screw guides the stock downwardly to the region oE the rotor vanes which then propel it outwardly against the walls of the tub. The higher consistency stock climbs the walls o the tub, and baf1es are employed to direct the pulp downwardly toward the tub center.
The potential advantages ox high censistency pulping devices have been well recognized. For example, since the density of the stock is consider-ably higher for pulp stock having a consistency of ; about 14% than for stock having a consistency of about 7~, the shear stresses created during a high consistency pulping operation are significantly greater, so that the time required to perform a pulping operation with high consistency stock may be the same or even less than the time required for `~ 35 pulping the same volume of low consistency stock in the same pulping tub.
,:
~23~6 lowever, there often exist inherent disad-vantages with high consistency pulping devices of the type previously described. For example, since the helical screw flight ox the feeding screw termi-nates above the base of the rotor and is spaced fromthe rotor vanes, there may exist a tendency for the high density stock to collect and form a wedge between the underside of the trailing portion of the screw flight and the portion of the rotor base immediately beneath it. Another disadvantage is that there does not exist means to guide the stock from the squared trailing portion of the screw flight to the working faces of the vanes, so that voids may be created surrounding the working faces of the vanes.
Accordingly, there is a need for a high consistency pulping apparatus having a rotor which minimizes the likelihood ox cavitation. There is al90 a need for a high consistency pulping apparatus in which the rotor provldes means for guiding the high density stock in a smooth and uninterrupted path from a location adjacent the center of the rotor to the working faces of the vanes without the stock becoming wedged between the screw slight and rotor vane The present invention provides an apparatus for pulping paper making stock which is capable of pulping relatively high consistency stock, that is, stock in a range of approximately 10-25% solids, in a manner that creates the necessary circular flow patterns to generate the high shear forces between paper particles in order to perform the pulping operation in a minimum amount of time. Another advantage of the invention is that it includes a rotor that is designed to minimiæe the likelihood of cavitation ancl the likelihood of stock collecting on .
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the rotor to obstruct the downward and outward flow of stock to the vanes.
According to one embodiment of the present invention, a rotor particularly adapted for use in pulping paper making stock at high consistencies is characterized by a rotor body adapted for mounting on a vertically extending drive shaft, a plurality of vanes extending outwardly from the rotor body, and a feed screw mounted centrally of the rotor body and extending upwardly therefrom. The feed screw has a conical body with helical flights extending along its length. When the rotor is rotated within a tub filled with paper making stock, the conical body and flights cooperate to guide stock downwardly and outwardly toward the vanes.
The downward and outward movement of the pulp resulting from the rotation of the weed screw causes the pulp to slow directly to the faces of the vanes and red-lces the likelihood of the stock col-lecting on the rotor between the feed screw and vanes. Furthermore, this elow path ensures that stock flows clownwardly between vines so that the entire face of each vane can provide the maximum pumping action for which it was designed.
In a preferred embodlment, the conical body of the feed screw includes a base sized such that its periphery is adjacent the root portions of the rotor vanes. The trailing end of the screw flight blends into the working face of a vane to form a continuous surface therewith. In another embodiment, the flight of the feed screw includes a trailing edge which tapers in width and terminates at the periphery of the base adjacent a vane root. Thus, the combination of the feed screw with the rotor ; 35 provides a guiding surface along which the stock mAy travel which extends from the upper tip of the feed screw to the outer tip of the rotoe vane.
: ;
, ~2~23~6 The present invention preferably ;ncludes a tub having a bottom wall and a cylindrical side wall extending upwardly therefrom, and the rotor body is centrally mounted on the bottom wall for rotation in a vertical axis.
The feed screw is sized such that, when mounted to the rotor body, its height above the bottom wall of the pulping tub approximates the intended depth of the stock within the tub. When rotated, the rotor of the preferred embodiment causes the stock within the tub to flow in the previously described circular pattern such that the level of the stock at the center of the tub is below the level of the stock at the side wall, thereby exposing the tip of the feed screw. When the Eeed screw and stock are in this configuration, the feed screw provides a means of escape for any air which is present in the vicinity of the vanes, thus further reducing the likelihood oE cavitation.
Another advantage of the construction of the present invention over prior art high consistency pulping devices is that the lnvention can utilize prior art rotors which previously were capable of functioning only in low consistency pulping opera-tions. By sizing the feed screw such that the periphery of the base and trailing portion of the flight are substantially contiguous with the faces of the vanes, the feed screw can be retrofitted to a prior art rotor, such as the rotor disclosed in the Couture U.S. Patent No. 3,88g,885. However, due to the nature of high consistency paper making stock, it is preferable although not necessary to utilize a ` rotor having between three and six vanes, since it is difficult to cause high consistency pulp to flow between the relatively narrow spaces existing between the vanes of rotors having more than six vanes. In 3~6 rotors having more than three of four vanes, it is also preferably to utilize a fced screw having multiple flights so that the stock can be urged downwardly and outwardly in a relatively balanced pattern about the periphery of the rotor.
Accordingly, it is an object of the present invention to provide an apparatus for pulping paper making stock at high consistencies which minimizes the likelihood of cavitation; an apparatus which provides a continuous path along which stock may travel from an upper portion of the pulping tub to the outer tip of the vane; and an apparatus for pulping high consistency stock which can be made by modifying low consistency systems.
Other objects and advantages of the present invention will become apparent from the hollowing description, the accompanying drawings and the appendecl claims. In order that the invention may be more readily understood, reference will now be made to the accompanying drawings, in which:
i Fig. 1 is a perspective view of the pulping apparatus of the preferred embodiment of the inven-tion in which the tub wall has been cut away to show the rotor;
Fig. 2 is a detail oE the rotor of Fig. l;
Fig. 3 is a side elevation in section of the tub of Fig. 1 showing the flow pattern of pulp stock during a pulping operation Fig. 4 is an alternate embodiment of the rotor of the invention; and Fig. 5 is another embodiment of a rotor of the invention.
i The pulper shown in Fig. 1 includes a tub I; 10 having a cylindrical upper wall 12 and a bottom wall comprising a plane center section 14 surrounded by a frusto-conical portion 16~ As shown in Fig. 2, ..
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Serial No. 448,340 -7-the center section 14 includes a perforated bed plate 18 for draining the pulped paper stock from the tub 10 after the completion of the pulping operation. The tub 10 is mounted on supports 20 above a gear drive 22 which is directly driven by a motor 24. The cylindrical side wall 12 incudes baffles 26 which direct pulp stock flowing upwardly against the wall outwardly toward the center of the tub 10.
A rotor, generally designated 28, is mounted in the center of the perforated bed plate 18 and is driven by the motor 24 and gear drive 22. The rotor 28 includes a rotor body 30 having a cover plate 32 and vane ring 34.
The vane ring 34 supports a plurality of vanes 36, alter-nate ones of which are of increased thickness and function as pumping vanes 38. The rotor ~28 as described thus far is of a type well-known in the art and is commonly used in pulping devices or defibering stock a between 5% and 8%
consistency. The structure and cooperation of the rotor 28 with the perorated bed plate 18 are described more ully in the Couture U.S. Patent No. 3,889,885.
However, the rotor 28 of the present invention differs significantly from prior art rotors in that it includes a feed screw, generally designated 40. The feed screw 40 includes a conical body 42 which is concentric with the rotor body 30, and extends upwardly therefrom.
The rotor 28 may be cast as a single unit, or the feed screw 40 and rotor body 30 may be fabricated separately and then joined together. The conical body 42 includes a rounded top 44 and a circular base 4~ which extends to the root portions 48 of the pumping vanes 38.
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The feed screw 40 includes helical screw flights 50, 52 which intertwine along the l.ength of the conical body 42. Each of the screw flights 50, 52 is ribbon-shaped and includes a trailinq portion 54 which terminates at the bass 46 of the conical body 42 adjacent the root ~8 of a vane 38. In the embodiment shown in Figs. 1 and 2, the trailing portions 54 are twisted so that their undersides 56 are contiguous with the face 58 of the pumping vane 38 so as to form a continuous surface therewith The operation of the pumping apparatus is best shown in Fig. 3. Prior to operation, the tub 10 is filled with paper making stock 60 which prefer-ably is at a consistency of between 12~ and 25~
solids. The level o the stock within the tub l0 should approximate the height of the rounded top 44 of the feed screw ~0 above the center section 14.
Once the tub 10 is willed, the rotor 28 is rotated in a countercloclcwise direction, indicated by arrows shown in Figs. 2 and 3. When the rotational speed j oE the rotor 28 has reached its intended operational speed, the helical screw flights sn, 52 of the feed screw 40 draw the stock 60 downwardly toward the rotor body 30. it the same time, the stock is urged outwardly by the lncreasing diameter oE the conical body 42. Thus, the stock travels in a downward helical path of increasing diameter, as indicated by arrows B in Fig. 3.
Since the base 46 of the helical body 42 and the trailing portions 54 of the screw flights are located adjacent the roots 48 of the vanes 38, the stock 60 is guided directly to the faces 58 of the pumping vanes 38. The downward and outward motion imparted to the stock 60 by the cooperation of the conical body 42 and flights 50, 52 places the stock down between the vanes 36 and 33 so that it I. .
g contacts the entire area of the vane face 58. Thus, the efficiency of the vanes 38 is increased since almost the entire vane face 58 contacts the pulp 60.
Once the pulp has contacted the vanes 38, it is propelled outwardly in a generally radial direction toward the frusto-conical portion 16, and then upwardly against the wall 12 to the top of the tub 10. The rising pulp encounters the baffles 26 which act to direct the pulp downwardly and inwardly toward the center of the tub where it again is directed toward the rotor body 30 by the feed screw 40. Due to the high consistency of the stock 60, the depth of the upwardly rising stock at the peri-phery of the tub 10 is greater than that at the tub center. Therefore, during operation, the rounded top 44 becosnes exposed and the feed screw provides a channel or conduit for the escape of air from the vicinity of the rotor body 30, thereby further reducing the likelihood of cavitation. It is to be understaod that the apparatus can be operated such that the depth of stock in the tub may exceed the height of the top 44, in which case the eeed screw 40 will convey air to the upper level of the stock, where it will escape through the remaining stock to the atmosphere.
With the embodiment shown in Figs. 1, 2 and 3, the conical body 42, the flights 50, 52 and the vane faces 58 combine to provide a substantially continuous pathway which positively guides the stock from the top of the feed screw 40 to the outer tips of the rotor vane faces 58. Since the trailing portions 54 of the screw flights blend into the vane faces 58, there are no pockets or gaps which may ;~ collect pulp or form voids, so that the generated flow of pulp is much smoother than with prior art rotors having feed screws whose flights are not contiguous with th. vane roots 48.
. , ~24;2346 One of the advantages of the present inven-tion is that a previously existiny low consistency pulpiny apparatus may be converted Jo perform the highly efficient high consistency pulping operation of the present invention with a minimum of expense.
For example, the rotor 28A shown in Fig. 4 includes a rotor body 30A in which a weed screw 40A has been attached to the cover plate 32A by a bolted flange 62 which extends outwardly from the peripherylbase 46A of the conical body 42A. The design of the rotor 28A differs from the rotor 28 shown in Figs.
1-3 in that the periphery of the base 46A is not immediately adjacent the vane roots 48A of the pumping vanes 38A. Furthermore, the trailing por-tions 54A of the screw fliyhts 50A, 52A are not contiguous with the vane roots 48A. Rather, the trailing portions 54A taper in width until they terminate at a point 64 locateci at the base 46A of the conical body 42A.
Since the feed screw 40A cannot be fabri-cated easily such that its trailing portions 5~A
blend into the vane faces 58A of the pre-existing rotor 2~A, it is desirable to taper the width of the trailiny portions to a point 64 to reduce the like-: 25 lihood that pulp stock will become wedged in the space between the underside of the trailing portions and the cover plate 32A or other portions of the rotor body 30A. Despite the fact that the conical body 42A and screw flights 50A, 52A are not immedi-ately adjacent the vane roots 48A, the feed screw 40A will still impart a downward and outward motion ' to the pulp stock within a tub which directs it to :~ the faces 5~3A of the vanes 3~A. This motion mini-: mizes the likelihood that pump stock will collect or stagnate in the central area of the rotor body 30A
and not flow to the pumping vanes 38A.
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~Z4Z34~
Another application of the invention is shown in Fig. 5 in which a rotor 28B includes a rotor body 30B having four vanes 36B, each of which includes a pumping face 58B. The vanes 36B are mounted on a generally frusto-conical shaped vane ring 34B. Rotor bodies 30B of this type are general-ly used in pulping operations where the consistency of the pulp stock is between 5% and 8~ solids.
A feed screw 40B is mounted to the central portion of the rotor body 30B and includes screw flights 50B, 52B which intertwine about the conical body 42B and terminate immediately adjacent the vane roots 48B. Each of the trailing portions 54B of the screw flights 50B, 52B taper in width in a manner similar to that of the embodiment of Fig. 4 and terminate at a point 64B on the base 46B of the conical body 42B.
Since the base 46B end points 64B are located immedlately adjacent the vane roots 48B, the outer edges 66 o the trailing portions 5qB cotnbine wlth the upper edges 68 oE the pumping faces 58B to orm continuous edges therewith. Ayain, while the trailing portions 54B ox the screw flights 50B, 52B
do not blend into the pumping Eaces 58B, the location of the trailing portions and the base 46B of the conical body 42B combine to provide a continuous path for the paper stock which guides the stock directly to the pumping faces 58B of the vanes 36B.
While the forms of apparatus herein ; 30 described constitute preferred embodiments of the 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 depart-ing from the scope of the invention as defined in the appended claims.
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APPARATUS FOR PULPING PAPER
This invention relates to apparatus for pulping paper making stock at relatively high con-sistencies, and more particularly to paper pulping apparatus in which a vaned rotor is utilized to circulate the stock within a tub.
Paper pulping apparatus typically includes a tub having a bottom wall and a cylindrical side wall extending upwardly therefrom, a vaned rotor centrally mounted on the bottom wall for rotation within the tub, and a screen or valve means located in or near the bottom wall to provide means for removal of the pulped paper stock. The rotor vanes include leading faces which are shaped and sized to contact stock near the bottom wall of the tub and propel it radially outwardly from the rotor against the side wall, which directs the stock upwardly.
The rising stock flows to the center of the tub and then downwardly toward the rotating vanes. Thus durin9 pulping operation, the stock is caused to flow in a generally clrcular pattern, and the reduc-tion in size of the individual particles of paper stock is due largely if not exclusively to the high sheer forces between particles of stock created by this flow pattern.
Many pulping devices of this construction presently in use are limited in application to paper making stock having a relatively low consistency, typically in the range of 4-7% solids content If the consistency of the stock is raised appreciably above about 7~, the density of viscosity of the stock is such that it does not easily flow downwardly between the spinning vanes of the rotor. The vanes will displace an initial quantity of pulp outwardly, but cavitation will when occur since the displaced pulp is not replaced by downwardly flowing pulp.
:
f ~4Z39~6 In order to perform a pulping process upon stock having a consistency in excess of about 10~, special rotors have been developed. For example, in the Blakly et al. U.S. Patent Application Serial No.
407,371, filed August 12,-1982 and commonly assigned, a high consistency pulping apparatus is disclosed having a rotor with a vertically oriented and axially aligned feeding screw. The rotor induces vanes in the form of circumferentially-extendin~ members with a half-crescent shape which are disposed about the periphery of a disk-shaped plate. The feeding screw is mounted in the center of the plate and includes a cylindrically-shaped body having a base which is spaced from the rotor vanes, and a helical screw flight which extends along the body and terminates at a squared end above the disk-shaped plate support-ing the vanes.
When rotated in a tub containing stock at 12-13% consistency, the feeding screw guides the stock downwardly to the region oE the rotor vanes which then propel it outwardly against the walls of the tub. The higher consistency stock climbs the walls o the tub, and baf1es are employed to direct the pulp downwardly toward the tub center.
The potential advantages ox high censistency pulping devices have been well recognized. For example, since the density of the stock is consider-ably higher for pulp stock having a consistency of ; about 14% than for stock having a consistency of about 7~, the shear stresses created during a high consistency pulping operation are significantly greater, so that the time required to perform a pulping operation with high consistency stock may be the same or even less than the time required for `~ 35 pulping the same volume of low consistency stock in the same pulping tub.
,:
~23~6 lowever, there often exist inherent disad-vantages with high consistency pulping devices of the type previously described. For example, since the helical screw flight ox the feeding screw termi-nates above the base of the rotor and is spaced fromthe rotor vanes, there may exist a tendency for the high density stock to collect and form a wedge between the underside of the trailing portion of the screw flight and the portion of the rotor base immediately beneath it. Another disadvantage is that there does not exist means to guide the stock from the squared trailing portion of the screw flight to the working faces of the vanes, so that voids may be created surrounding the working faces of the vanes.
Accordingly, there is a need for a high consistency pulping apparatus having a rotor which minimizes the likelihood ox cavitation. There is al90 a need for a high consistency pulping apparatus in which the rotor provldes means for guiding the high density stock in a smooth and uninterrupted path from a location adjacent the center of the rotor to the working faces of the vanes without the stock becoming wedged between the screw slight and rotor vane The present invention provides an apparatus for pulping paper making stock which is capable of pulping relatively high consistency stock, that is, stock in a range of approximately 10-25% solids, in a manner that creates the necessary circular flow patterns to generate the high shear forces between paper particles in order to perform the pulping operation in a minimum amount of time. Another advantage of the invention is that it includes a rotor that is designed to minimiæe the likelihood of cavitation ancl the likelihood of stock collecting on .
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the rotor to obstruct the downward and outward flow of stock to the vanes.
According to one embodiment of the present invention, a rotor particularly adapted for use in pulping paper making stock at high consistencies is characterized by a rotor body adapted for mounting on a vertically extending drive shaft, a plurality of vanes extending outwardly from the rotor body, and a feed screw mounted centrally of the rotor body and extending upwardly therefrom. The feed screw has a conical body with helical flights extending along its length. When the rotor is rotated within a tub filled with paper making stock, the conical body and flights cooperate to guide stock downwardly and outwardly toward the vanes.
The downward and outward movement of the pulp resulting from the rotation of the weed screw causes the pulp to slow directly to the faces of the vanes and red-lces the likelihood of the stock col-lecting on the rotor between the feed screw and vanes. Furthermore, this elow path ensures that stock flows clownwardly between vines so that the entire face of each vane can provide the maximum pumping action for which it was designed.
In a preferred embodlment, the conical body of the feed screw includes a base sized such that its periphery is adjacent the root portions of the rotor vanes. The trailing end of the screw flight blends into the working face of a vane to form a continuous surface therewith. In another embodiment, the flight of the feed screw includes a trailing edge which tapers in width and terminates at the periphery of the base adjacent a vane root. Thus, the combination of the feed screw with the rotor ; 35 provides a guiding surface along which the stock mAy travel which extends from the upper tip of the feed screw to the outer tip of the rotoe vane.
: ;
, ~2~23~6 The present invention preferably ;ncludes a tub having a bottom wall and a cylindrical side wall extending upwardly therefrom, and the rotor body is centrally mounted on the bottom wall for rotation in a vertical axis.
The feed screw is sized such that, when mounted to the rotor body, its height above the bottom wall of the pulping tub approximates the intended depth of the stock within the tub. When rotated, the rotor of the preferred embodiment causes the stock within the tub to flow in the previously described circular pattern such that the level of the stock at the center of the tub is below the level of the stock at the side wall, thereby exposing the tip of the feed screw. When the Eeed screw and stock are in this configuration, the feed screw provides a means of escape for any air which is present in the vicinity of the vanes, thus further reducing the likelihood oE cavitation.
Another advantage of the construction of the present invention over prior art high consistency pulping devices is that the lnvention can utilize prior art rotors which previously were capable of functioning only in low consistency pulping opera-tions. By sizing the feed screw such that the periphery of the base and trailing portion of the flight are substantially contiguous with the faces of the vanes, the feed screw can be retrofitted to a prior art rotor, such as the rotor disclosed in the Couture U.S. Patent No. 3,88g,885. However, due to the nature of high consistency paper making stock, it is preferable although not necessary to utilize a ` rotor having between three and six vanes, since it is difficult to cause high consistency pulp to flow between the relatively narrow spaces existing between the vanes of rotors having more than six vanes. In 3~6 rotors having more than three of four vanes, it is also preferably to utilize a fced screw having multiple flights so that the stock can be urged downwardly and outwardly in a relatively balanced pattern about the periphery of the rotor.
Accordingly, it is an object of the present invention to provide an apparatus for pulping paper making stock at high consistencies which minimizes the likelihood of cavitation; an apparatus which provides a continuous path along which stock may travel from an upper portion of the pulping tub to the outer tip of the vane; and an apparatus for pulping high consistency stock which can be made by modifying low consistency systems.
Other objects and advantages of the present invention will become apparent from the hollowing description, the accompanying drawings and the appendecl claims. In order that the invention may be more readily understood, reference will now be made to the accompanying drawings, in which:
i Fig. 1 is a perspective view of the pulping apparatus of the preferred embodiment of the inven-tion in which the tub wall has been cut away to show the rotor;
Fig. 2 is a detail oE the rotor of Fig. l;
Fig. 3 is a side elevation in section of the tub of Fig. 1 showing the flow pattern of pulp stock during a pulping operation Fig. 4 is an alternate embodiment of the rotor of the invention; and Fig. 5 is another embodiment of a rotor of the invention.
i The pulper shown in Fig. 1 includes a tub I; 10 having a cylindrical upper wall 12 and a bottom wall comprising a plane center section 14 surrounded by a frusto-conical portion 16~ As shown in Fig. 2, ..
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Serial No. 448,340 -7-the center section 14 includes a perforated bed plate 18 for draining the pulped paper stock from the tub 10 after the completion of the pulping operation. The tub 10 is mounted on supports 20 above a gear drive 22 which is directly driven by a motor 24. The cylindrical side wall 12 incudes baffles 26 which direct pulp stock flowing upwardly against the wall outwardly toward the center of the tub 10.
A rotor, generally designated 28, is mounted in the center of the perforated bed plate 18 and is driven by the motor 24 and gear drive 22. The rotor 28 includes a rotor body 30 having a cover plate 32 and vane ring 34.
The vane ring 34 supports a plurality of vanes 36, alter-nate ones of which are of increased thickness and function as pumping vanes 38. The rotor ~28 as described thus far is of a type well-known in the art and is commonly used in pulping devices or defibering stock a between 5% and 8%
consistency. The structure and cooperation of the rotor 28 with the perorated bed plate 18 are described more ully in the Couture U.S. Patent No. 3,889,885.
However, the rotor 28 of the present invention differs significantly from prior art rotors in that it includes a feed screw, generally designated 40. The feed screw 40 includes a conical body 42 which is concentric with the rotor body 30, and extends upwardly therefrom.
The rotor 28 may be cast as a single unit, or the feed screw 40 and rotor body 30 may be fabricated separately and then joined together. The conical body 42 includes a rounded top 44 and a circular base 4~ which extends to the root portions 48 of the pumping vanes 38.
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The feed screw 40 includes helical screw flights 50, 52 which intertwine along the l.ength of the conical body 42. Each of the screw flights 50, 52 is ribbon-shaped and includes a trailinq portion 54 which terminates at the bass 46 of the conical body 42 adjacent the root ~8 of a vane 38. In the embodiment shown in Figs. 1 and 2, the trailing portions 54 are twisted so that their undersides 56 are contiguous with the face 58 of the pumping vane 38 so as to form a continuous surface therewith The operation of the pumping apparatus is best shown in Fig. 3. Prior to operation, the tub 10 is filled with paper making stock 60 which prefer-ably is at a consistency of between 12~ and 25~
solids. The level o the stock within the tub l0 should approximate the height of the rounded top 44 of the feed screw ~0 above the center section 14.
Once the tub 10 is willed, the rotor 28 is rotated in a countercloclcwise direction, indicated by arrows shown in Figs. 2 and 3. When the rotational speed j oE the rotor 28 has reached its intended operational speed, the helical screw flights sn, 52 of the feed screw 40 draw the stock 60 downwardly toward the rotor body 30. it the same time, the stock is urged outwardly by the lncreasing diameter oE the conical body 42. Thus, the stock travels in a downward helical path of increasing diameter, as indicated by arrows B in Fig. 3.
Since the base 46 of the helical body 42 and the trailing portions 54 of the screw flights are located adjacent the roots 48 of the vanes 38, the stock 60 is guided directly to the faces 58 of the pumping vanes 38. The downward and outward motion imparted to the stock 60 by the cooperation of the conical body 42 and flights 50, 52 places the stock down between the vanes 36 and 33 so that it I. .
g contacts the entire area of the vane face 58. Thus, the efficiency of the vanes 38 is increased since almost the entire vane face 58 contacts the pulp 60.
Once the pulp has contacted the vanes 38, it is propelled outwardly in a generally radial direction toward the frusto-conical portion 16, and then upwardly against the wall 12 to the top of the tub 10. The rising pulp encounters the baffles 26 which act to direct the pulp downwardly and inwardly toward the center of the tub where it again is directed toward the rotor body 30 by the feed screw 40. Due to the high consistency of the stock 60, the depth of the upwardly rising stock at the peri-phery of the tub 10 is greater than that at the tub center. Therefore, during operation, the rounded top 44 becosnes exposed and the feed screw provides a channel or conduit for the escape of air from the vicinity of the rotor body 30, thereby further reducing the likelihood of cavitation. It is to be understaod that the apparatus can be operated such that the depth of stock in the tub may exceed the height of the top 44, in which case the eeed screw 40 will convey air to the upper level of the stock, where it will escape through the remaining stock to the atmosphere.
With the embodiment shown in Figs. 1, 2 and 3, the conical body 42, the flights 50, 52 and the vane faces 58 combine to provide a substantially continuous pathway which positively guides the stock from the top of the feed screw 40 to the outer tips of the rotor vane faces 58. Since the trailing portions 54 of the screw flights blend into the vane faces 58, there are no pockets or gaps which may ;~ collect pulp or form voids, so that the generated flow of pulp is much smoother than with prior art rotors having feed screws whose flights are not contiguous with th. vane roots 48.
. , ~24;2346 One of the advantages of the present inven-tion is that a previously existiny low consistency pulpiny apparatus may be converted Jo perform the highly efficient high consistency pulping operation of the present invention with a minimum of expense.
For example, the rotor 28A shown in Fig. 4 includes a rotor body 30A in which a weed screw 40A has been attached to the cover plate 32A by a bolted flange 62 which extends outwardly from the peripherylbase 46A of the conical body 42A. The design of the rotor 28A differs from the rotor 28 shown in Figs.
1-3 in that the periphery of the base 46A is not immediately adjacent the vane roots 48A of the pumping vanes 38A. Furthermore, the trailing por-tions 54A of the screw fliyhts 50A, 52A are not contiguous with the vane roots 48A. Rather, the trailing portions 54A taper in width until they terminate at a point 64 locateci at the base 46A of the conical body 42A.
Since the feed screw 40A cannot be fabri-cated easily such that its trailing portions 5~A
blend into the vane faces 58A of the pre-existing rotor 2~A, it is desirable to taper the width of the trailiny portions to a point 64 to reduce the like-: 25 lihood that pulp stock will become wedged in the space between the underside of the trailing portions and the cover plate 32A or other portions of the rotor body 30A. Despite the fact that the conical body 42A and screw flights 50A, 52A are not immedi-ately adjacent the vane roots 48A, the feed screw 40A will still impart a downward and outward motion ' to the pulp stock within a tub which directs it to :~ the faces 5~3A of the vanes 3~A. This motion mini-: mizes the likelihood that pump stock will collect or stagnate in the central area of the rotor body 30A
and not flow to the pumping vanes 38A.
., , .
~Z4Z34~
Another application of the invention is shown in Fig. 5 in which a rotor 28B includes a rotor body 30B having four vanes 36B, each of which includes a pumping face 58B. The vanes 36B are mounted on a generally frusto-conical shaped vane ring 34B. Rotor bodies 30B of this type are general-ly used in pulping operations where the consistency of the pulp stock is between 5% and 8~ solids.
A feed screw 40B is mounted to the central portion of the rotor body 30B and includes screw flights 50B, 52B which intertwine about the conical body 42B and terminate immediately adjacent the vane roots 48B. Each of the trailing portions 54B of the screw flights 50B, 52B taper in width in a manner similar to that of the embodiment of Fig. 4 and terminate at a point 64B on the base 46B of the conical body 42B.
Since the base 46B end points 64B are located immedlately adjacent the vane roots 48B, the outer edges 66 o the trailing portions 5qB cotnbine wlth the upper edges 68 oE the pumping faces 58B to orm continuous edges therewith. Ayain, while the trailing portions 54B ox the screw flights 50B, 52B
do not blend into the pumping Eaces 58B, the location of the trailing portions and the base 46B of the conical body 42B combine to provide a continuous path for the paper stock which guides the stock directly to the pumping faces 58B of the vanes 36B.
While the forms of apparatus herein ; 30 described constitute preferred embodiments of the 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 depart-ing from the scope of the invention as defined in the appended claims.
, :
Claims (2)
1. Apparatus for pulping paper making stock at high consistencies in the range of 10-25% solids, comprising:
(a) a pulper tub having a bottom wall, an annular perforated bed plate forming a portion of said bottom wall, a cylindrical side wall and a frustoconical wall extending upwardly from said bottom wall to said side wall, (b) a rotor body of a smaller outer diameter than said bed plate mounted for rotation on a vertical axis in the center of said bottom wall, (c) pulping vanes extending generally radially outwardly from and beyond said rotor body in overhanging relation with said bed plate and in circumferentially spaced relation with each other to provide spaces therebetween exposing portions of said bed plate, (d) said rotor body also including pumping vanes above said pulping vanes, (e) means for rotating said rotor at sufficient velocity to cause said pulping vanes to impel high consistency pulp stock outwardly therefrom toward said frustoconical wall with sufficient force to climb said wall, (f) a feed screw mounted centrally of said rotor body and extending upwardly therefrom, (g) said feed screw having a conical body and helical flight means extending along said body, (h) said conical screw body including a base so proportioned as to cover a substantial portion of the center of said rotor body and having the periphery thereof adjacent the root portions of said pumping vanes whereby when said rotor is rotated, said flight means and said conical body cooperate to urge the stock downwardly and outwardly directly through the spaces between said pumping vanes to said exposed portions of said bed plate, (i) said pumping vanes including substantially vertically extending leading faces, (j) said flight means including flat undersides, and (k) a trailing portion of each of said flight means being contiguous with one of said pumping vane faces such that said undersides and said faces form substantially continuous guide surfaces wherein higher consistency stock urged downwardly and outwardly by said screw is guided to said pulping vanes along said guide surface means.
(a) a pulper tub having a bottom wall, an annular perforated bed plate forming a portion of said bottom wall, a cylindrical side wall and a frustoconical wall extending upwardly from said bottom wall to said side wall, (b) a rotor body of a smaller outer diameter than said bed plate mounted for rotation on a vertical axis in the center of said bottom wall, (c) pulping vanes extending generally radially outwardly from and beyond said rotor body in overhanging relation with said bed plate and in circumferentially spaced relation with each other to provide spaces therebetween exposing portions of said bed plate, (d) said rotor body also including pumping vanes above said pulping vanes, (e) means for rotating said rotor at sufficient velocity to cause said pulping vanes to impel high consistency pulp stock outwardly therefrom toward said frustoconical wall with sufficient force to climb said wall, (f) a feed screw mounted centrally of said rotor body and extending upwardly therefrom, (g) said feed screw having a conical body and helical flight means extending along said body, (h) said conical screw body including a base so proportioned as to cover a substantial portion of the center of said rotor body and having the periphery thereof adjacent the root portions of said pumping vanes whereby when said rotor is rotated, said flight means and said conical body cooperate to urge the stock downwardly and outwardly directly through the spaces between said pumping vanes to said exposed portions of said bed plate, (i) said pumping vanes including substantially vertically extending leading faces, (j) said flight means including flat undersides, and (k) a trailing portion of each of said flight means being contiguous with one of said pumping vane faces such that said undersides and said faces form substantially continuous guide surfaces wherein higher consistency stock urged downwardly and outwardly by said screw is guided to said pulping vanes along said guide surface means.
2. A rotor assembly as defined in claim 1 wherein said feed screw body is substantially equal in height to twice the maximum radius of said vanes.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US47084783A | 1983-02-28 | 1983-02-28 | |
| US470,847 | 1990-01-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1242346A true CA1242346A (en) | 1988-09-27 |
Family
ID=23869305
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000448340A Expired CA1242346A (en) | 1983-02-28 | 1984-02-27 | Apparatus for pulping paper |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0117716B1 (en) |
| JP (1) | JPS59199895A (en) |
| BR (1) | BR8400776A (en) |
| CA (1) | CA1242346A (en) |
| DE (1) | DE3473894D1 (en) |
| ES (1) | ES530083A0 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1228762A (en) * | 1983-05-18 | 1987-11-03 | Joseph W. Couture | Pulping apparatus and method |
| DE3743247A1 (en) * | 1987-12-19 | 1989-06-29 | Escher Wyss Gmbh | PULPER WITH HIGH RESOLUTION EFFICIENCY |
| SE509293C2 (en) | 1997-04-29 | 1999-01-11 | Cellwood Machinery Ab | Device at mass solver |
| ITVI20020048A1 (en) * | 2002-03-19 | 2003-09-19 | Comer Spa | PROPULSOR FOR THE STIRRING OF SUSPENSIONS OF SOLIDS INSIDE A TREATMENT TANK |
| GB0703053D0 (en) | 2007-02-16 | 2007-03-28 | Ici Plc | Apparatus for and Methods of Mixing and Dispensing Samples |
| CN101708819B (en) * | 2008-12-03 | 2012-07-04 | 鞍钢集团矿业公司 | Ore pulp distributer |
| DE102010005596B4 (en) | 2010-01-25 | 2015-11-05 | Epcos Ag | Electroacoustic transducer with reduced losses due to transversal emission and improved performance by suppression of transverse modes |
| DE102011082976A1 (en) | 2011-09-19 | 2013-03-21 | Günter Betz | Device for breaking up (shredding, shredding, dissolving, processing) of waste paper and pulp in a pulper (pulper) |
| AT517870B1 (en) * | 2015-10-30 | 2019-03-15 | Chemiefaser Lenzing Ag | High concentration mixer for producing a cellulosic suspension with high cellulose concentration |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3171606A (en) * | 1962-06-06 | 1965-03-02 | Ed Jones Corp | Circulating and disintegrating rotor for pulping apparatus |
| GB1176412A (en) * | 1967-01-26 | 1970-01-01 | Bolton Emerson | Improvements in and relating to an apparatus and method for Pulping and Defibering |
| JPS5225104A (en) * | 1975-08-14 | 1977-02-24 | Bolton Emerson | Pulp making method |
| DE2542065A1 (en) * | 1975-09-20 | 1977-03-24 | Bolton Emerson | Vortical circulation fibre refining pulper - treats unconventional materials by advancing rotor to zero clearance from stator |
| DE2917814C2 (en) * | 1979-05-03 | 1983-12-08 | J.M. Voith Gmbh, 7920 Heidenheim | Pulpers for the production of paper stock suspensions |
| DE3027044C2 (en) * | 1980-07-17 | 1982-12-16 | J.M. Voith Gmbh, 7920 Heidenheim | Rotor for a pulper |
-
1984
- 1984-02-21 BR BR8400776A patent/BR8400776A/en unknown
- 1984-02-22 EP EP19840301139 patent/EP0117716B1/en not_active Expired
- 1984-02-22 DE DE8484301139T patent/DE3473894D1/en not_active Expired
- 1984-02-27 CA CA000448340A patent/CA1242346A/en not_active Expired
- 1984-02-27 ES ES530083A patent/ES530083A0/en active Granted
- 1984-02-28 JP JP3721584A patent/JPS59199895A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| EP0117716A2 (en) | 1984-09-05 |
| ES8503050A1 (en) | 1985-02-01 |
| JPH055958B2 (en) | 1993-01-25 |
| DE3473894D1 (en) | 1988-10-13 |
| EP0117716B1 (en) | 1988-09-07 |
| JPS59199895A (en) | 1984-11-13 |
| EP0117716A3 (en) | 1985-05-29 |
| BR8400776A (en) | 1984-10-02 |
| ES530083A0 (en) | 1985-02-01 |
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