US3460466A - Press structure - Google Patents

Description

Aug. 12, 1969 G|NAVEN ET AL 3,460,466

PRESS STRUCTURE Filed Dec. 14. 1965 2' Sheets-*Sheet 1 34 NVENTORJ ATTORNEY M. E. GINAVEN ETAL 3,460,466 PRESS STRUCTURE 2 Sheets-Sheet 2 Aug. 12, Filed Dec. 14. 1965' mvsmons my ewut. 4/04 ww 428cm- :4. non:

Y yam-re Paw ATTORNEY United States Patent 3,460,466 PRESS STRUCTURE Marvin E. Ginaven and Albert H. Adams, Springfield, Ohio, assignors to The Bauer Bros. (10., Springfield, Ohio, a corporation of Ohio Filed Dec. 14, 1965, Ser. No. 513,718 Int. Cl. B30b 9/12, 9/14, 9/18 US. Cl. 100-117 9 Claims ABSTRACT OF THE DISCLOSURE This invention relates to pulp processing and like arts and has particular although not limited reference to an economical system and apparatus for increasing the percent of solids in a flowing pulp slurry.

The invention has in view the use of dewatering or like press means to produce an improved pulp preparation, as for example the conditioning of pulp to a degree enabling a more effective working in a pulp refiner.

A primary object of the invention is to provide improvements in systems and equipment for pulp preparation which are economical to fabricate and which render such systems more efficient and satisfactory in use, more adaptable to a wide variety of applications and less likely to malfunction.

An additional object of the invention is to achieve, in a dewatering or like press, a dryer end product with no added power consumption.

Another object of the invention is to reduce operating pressure in a dewatering or like press means whereby to lessen power requirements and avoid wear and damage to the equipment without loss of its thickening efficiency.

A further object of the invention is to introduce an improved dewatering press using a cross screw for output control, wherein the cross screw serves, additionally, as a second stage means to express fluids.

Still another object of the invention is to introduce a generally improved press providing a two stage draining process whereby to achieve an end product having greater dryness and requiring less power consumption.

A further object of the invention is to provide an improved dewatering or like press possessing the advantageous structural features, the inherent meritorious characteristics and the means and mode of use herein described.

With the above and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

Referring to the accompanying drawing wherein is shown one but obviously not necessarily the only form of embodiment of the invention.

FIG. 1 is a generally schematic top view, in longitudinal section, of a dewatering or like press in accordance with a preferred embodiment of the invention;

FIG. 2 is a fragmentary elevation view of the device of FIG. 1; and

FIG. 3 is a diagram showing the relationship of percent solids in a kraft pulp to the unit pressure on the pulp.

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Referring to the drawings, the invention, in its illustrative embodiment is comprised of apparatus facilitating the thickening of pulp material in the course of its movement in liquid suspension to refiners or like treating equipment. In the working of pulp it frequently becomes necessary to change the consistency of the pulp-liquid mixture. For screening and cleaning, the pump is usually carried as a very low percentage of solids in a fluid vehicle. After screening and cleaning, a pulp treatment process conventionally provides a refining step. For effective refining the pulp consistency must be increased. In a typical commercial installation for this purpose it may be desirable, for example, to increase the percent of solids in a flowing slurry from about. 5% to about 30%. When pulp is to be placed in storage, it is desirable here also to increase the pulp consistency to the maximum at which the material can be pumped.

Thickening apparatus in accordance with the present invention would, in such a pulp handling system as described, be arranged to receive screened and cleaned pulp, thicken it to a selected consistency and then direct it to refiners or to a storage chest in accordance with its work requirements. Supply to a refiner is accomplished under pressure whereby to increase the refiner capacity and the versatility of its work.

It will be recognized that the invention apparatus, as disclosed, is capable of handling a wide variety of materials and can be used advantageously in the preparation of pulp for other than the paper industry. Similarly, it is not limited in function to acting as a pressure feeder but has general application as dewatering or low pressure washing means. In the latter case water or other liquid is introduced to and mixed with the pulp before its entry into the invention system and is there drained to eliminate unwanted solids in a most effective manner.

The illustrated embodiment of the invention takes the form of a unitary machine forming a part of a continuous pulp treatment system. The machine is stationed to receive watered pulp material and to place the material under pressure in a two stage process draining excess liquid therefrom and delivering the dewatered or thickened pulp to a subsequent processing stage.

The invention apparatus, as disclosed, is comprised of essentially continuous relatively staged press means. It includes a housing rassembly made up of a plurality of interconnected parts resting on a base 10. At one end of the assembly is a gear box 11. The box 11 contains meshing gears 12 and 13 which respectively mount on shafts 14 and 15. The latter are disposed parallel to one another and in a vertically spaced generally parallel relation to the base 10. The one end of shaft 15 projects outwardy of the box 11 for cooperation with powered drive means such as an electric motor (not shown). Projecting inwardly of the housing assembly, through and beyond the gear box 11, the shafts 14 and 15 are disposed in a press cage 16 comprised in part of bars 16' extending in radially spaced parallel relation to the shafts and arranged in a generally cylindrical pattern. The bars may be spaced circumferentially in accordance with known construction to provide drainage slots therebetween. Details of this are not shown since in and of themselves they form no part of the present invention. The arrangement of bars 16' is held together by a longitudinally spaced series of circumferential clamp members 17 each secured in known manner by a bolt 18. As indicated, the bars 16 may be comprised of a plurality of longitudinally aligned sets of bars separated and interconnected. by spacers 19, the latter forming a part of a casing or shroud 21 which partly surrounds the press cage.

Sleeve mounted helicoid screw means 22 and 23 are fixedly disposed on the respective shafts 14 and 15 in a manner to have their screw flights in an interfitting relation to one another. Further, the marginal edges of such screw flights approach a contacting relation to the cage wall defined by inner surfaces of the bars 16. In this way the advance of wet bulk material through the press cage is made a function of rotation of the feed screw means as represented by the devices 22 and 23. The twin screws extend throughout the length of the press cage.

The cage inlet 24 is adjacent to the gear box 11 while its outlet accommodates the projection therethrough of the remote ends of shafts 14 and 15.

At their outer ends the shafts 14 and 15 have extensions projected through the cage end plate 25. These extensions respectively mount feed screw extensions 22a and 23a which form continuations of the screw device 22 and 23. Extensions 22a and 23a lie within a tubular enclosure 26, a flanged end of which is fixed in abutting secured relation to the end plate 25.

The enclosure 26 extends from and is a part of a housing 27 disposed at right angles to the press cage. This en closure contains second stage feed screw means in the form of a helicoid device 28 mounted on a shaft 29. The shaft 29 extends through and longitudinally of the housing 27 in a manner to place screw means 28 thereon in a transverse intersecting relation to the discharge from the helicoid devices 22 and 23 and their extensions. At its opposite ends the housing 27 includes bearings for the shaft 29, and, near what may he considered the discharge end thereof provides further a discharge opening 31, indicated diagrammatically in broken lines. A longitudinal housing through passage 32 accommodates the shaft 29 and the screw means 28 thereon, the peripheral edge of the screw flights approaching a contacting relation to the passage Wall.

Enclosure 26 opens at right angles to one end of the passage 32. In the region of such enclosure, and for a short distance there-beyond toward discharge opening 31, the passage 32 is circumferentially enlarged to form a secondary dewatering chamber 33. In such enlarged section, a hemicylindrical underpart of housing 27 provides a drainer section 34. The latter is comprised of bars or wedge-wires 35 circumferentially spaced like the bars 16' and contained by circumferential clamps 36. Thus, the drainer section 34 extends the length of chamber 33 and occupies approximately half the circumference of the housing 27 in this area. Within the housing 27 the feed screw means 28 passes over the drainer section and, as described, in a sense at right angles to the adjacent ends of the shafts 14 and 15 and the helicoid devices which mount thereon.

One end of the shaft 29 projects through and beyond the housing 27 for engagement by suitable means for powered rotation of the shaft. In accordance with the preferred mode of operation, shaft 29 is driven independently of shafts 14 :and 15 in order that its speed of rotation may be relatively varied.

The apparatus of the invention thus described provides for a two stage pressured feeding of a pulp slurry, with drainage of released liquids occurring in each stage. The flowing slurry entering the cage 16 at inlet opening 24 loses some of its fluids due to a gravity fiow while others are pressure expressed as the material is advanced through the cage by the overlapped twin screw means 2223. The fluids released in this first stage escape between the bars 16 which define a principal drainer section intermediate the inlet and outlet of the press cage.

Enclosure 26 serves as an adapter section, the wet bulk material advanced Iby the screws 22 and 23 being picked up by extensions 22a and 23a and propelled thereby through section 26 into the housing unit 27. The materials discharge into chamber 33 to be immediately picked up by the relatively right angled screw means 28. The materials are then advanced to and through passage 32 and a choke 37, and discharged from the thus provided second stage of the invention system by way of the discharge opening 31. Pressure applied to the material by the device 28 produces a release of additional fluids which are permitted to escape from the apparatus by Way of drainer section 34.

The feed screw means 28 operates to create a back pressure and further, to vary the back pressure exerted on the materials advanced by the twin feed screw means 22 and 23. It serves to provide also a positive discharge of considerably thickened material from opening 31. Additionally, and in accordance with the present inventive concept, it achieves a secondary dewatering of the pulp material for optimal dryness thereof and in a manner to relieve the pressures which otherwise occur in the cage 16 and adapter section 26.

In the latter regard there is a known relationship between the percent of solids resulting in a given pulp material and the unit pressure applied to the pulp. As shown in FIG. 3, which diagrammatically indicates the conditions of an application of pressure to a kraft material, gravity drainage thickens a pulp to about 8% solids. Thereafter, increases in unit pressure thereon induce rapid drainage until a level of about 30% solids is reached, whereupon as the curve indicates, change becomes quite gradual. As shown, whereas an increase in consistency to 30% solids can he achieved by an applied pressure on the order of 35 pounds, an increase to 50% solids is not feasible unless pressures reach a range of 8,000 to 10,000 p.s.1.

The twin screw feeding devices 22 and 23 and their extensions develop a maximum pressure at the end thereof where a change in flow direction takes place and the feed screw means 28 exerts back pressure. To achieve a pressure level along the length of the devices 22 and 23 adequate to produce at their ends a pulp consistency of 30% solids it has been found in practice that without the invention improvements the pressures at the outlet end of the twin screws have to :be substantially higher than the 35 pounds indicated by the diagram of FIG. 3 as required for this purpose. This higher pressure serves no useful purpose in dewatering. It is actually disadvantageous due to the resulting wear and stress on the equipment and the fact that under such conditions the component parts of the press must be built sufficiently heavy and strong to withstand such pressure.

By use of the instant invention one provides relief of such presures as would normally be required at the outlet end of the twin screws. In a secondary dewatering procedure the drainer section 34 utilizes pressure created by screw 28 to express fluids from the pulp entering the housing 27. In the process, formation of a plug occurs in what may be considered the choke section 37 of passage 32 immediately preceding opening 31. Therefore, a final dryness of the pulp material to the desired consistency is achieved in the housing 27, the pressures mak ing this possible being a function of rotation of the shaft 29 and largely independent of the twin screw means 2223. Due to utilizing pressure developed by screw 28 in a secondary dewatering procedure screw means 2223 operate against less back pressure and therefore function under relatively reduced pressure conditions throughout their length. This results in a substantial reduction in torque while achieving the necessary end product by using the second stage dewaterin'g section of the equipment. As a consequence there is a saving in horsepower and much less wear and tear on the equipment.

Tests run on a dewatering press of the instant type without cross screw drainage show a typical power input for a normal capacity to be in the range of .9 to 1.1 H.P. days per ton on the unbleached kraft pulp to obtain 30% solids. By utilizing cross screw drainage as described the power usage drops to about .5 HP. days per ton to achieve 30% solids end products.

In summary, by utilizing the drainer section 34 as described the pressure on the outlet ends of the screws 22-23 is reduced, the pressure in the drainer portion of the twin screw section is reasonable, and the overall torque on the screws is reduced. Also, as compared to approximately 1 HF. days per ton by using the present invention the power usage on a kraft pulp has been observed to be about .5 H.P. days per ton to achieve 30% solids, a horsepower savings of approximately 50% over the prior art.

The invention accordingly affords numerous advantages. Since the pressures in the twin screw section are reduced a press can be designed more economically and a lighter press construction can be utilized. Horsepower consump tion can be very substantially reduced in achieving the same degree of thickening as achieved by more expensive equipment of the prior art. Also, greater dryness of end products can be obtained than would be obtained in a press without cross screw drainage. Further, excessive friction and wear in the twin screw section, caused by screws being subjected to high level terminal pressures are obviated.

Considering the invention in the light of fluids removed, it is known from experience and by the chart of FIG. 3 that pressures of about 25 psi. will dewater most pulps to about 20% solids from a pumpable slurry. With the invention, the high volume of liquid to be removed can readily be handled in the twin screw section. For example, in dewatering 100 tons of a pulp slurry in twenty-four hours, having a solids content of 5%, to a solids content of 30% then it is necessary to remove approximately 250 gal-ions per minute of liquid from an original feed rate of 300 gallons per minute. To go from 5% solids to 20% means a removal of 225 gallons per minute. In the two step continuous operation of the instant invention one can with low power and high volumes more effectively use the twin screw section. In the case of a 100 ton per day operation, drainage in the low pressure primary dewatering section would occur at a rate of about 225 gallons per minute. With the material compacted and at about 20% solids the higher pressure single feed screw means 28 becomes, in conjunction with drainer section 34, a secondary dewatering means which need remove only 25 gallons per minute to achieve the desired 30% solids consistency.

It is to be understood the cross screw drainage concept may also be used with a single screw means at the low pressure end of the press, as now defined by the twin screw means 22-23. However twin screws have certain advantages over a single screw, as for example in their ability to accept and move aslurry of very low consistency.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise lbut one of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described our invention we claim:

1. A dewatering or like press structure, including a main press cage having an inlet thereto and an outlet therefrom and incorporating feed screw means for advancing a pulp slurry to move from said inlet to and through said outlet, said screw means being formed to extract fluid from the pulp slurry during its movement through said cage, said cage being formed to drain said extracted fluids, characterized by a discharge housing in connection with and forming a continuation of said cage on a common level, said housing providing a discharge passage in direct communication with and extending angularly across said cage outlet, means defining an inlet to the discharge passage of said housing connecting to rim said cage outlet, said housing having at its end remote from the cage outlet a limited opening for discharge of pulp from the terminal portion of said passage, independent feed screw means rotatable in said passage, said means defining said inlet to said housing discharge passage having extended therein transfer means connected with said feed screw means to pressure feed the thickened slurry delivered from said cage into said discharge passage in a continuous flow, said transfer means extending to said discharge passage immediately adjacent said independent feed screw means for immediate and direct pickup of the pulp material thereby to move it through said discharge passage in a continuous flow and change the direction of its flow, said independent feed screw means being formed and operable to apply a selected back pressure on said transfer means and further compress the materials in the thickened slurry in the process of positively moving the resultant pulp product to and through said discharge opening, and said housing in the area thereof immediately adjacent said transfer means incorporating means for further draining and thereby relieving pressure on the material delivered to said housing to provide that said screw means and said press operate under minimal pressure without loss of operating efficiency and that a relatively high consistency pulp product is discharged from said housing.

2. A press as in claim 1 characterized by said first mentioned feed screw means consisting of a pair of screw units having screw flights in overlapped interfitting cooperative relation.

3. A dewa-tering or like press according to claim 2 characterized in that said housing incorporates a choke in said passage in immediate advance of said discharge opening where said independent feed screw means causes the formation of a relatively dry plug of the thickened materials resulting from said pulp slurry.

4. A dewatering or like press according to claim 1 characterized in that said last mentioned drain means consists of an underportion of said housing providing an enlargement of said passage in the area of its inlet and being formed with slots underlying at least a portion of said independent feed screw means.

5. A dewatering or like press according to claim 1 characterized in that said transfer means is provided by a direct extension of the first-mentioned feed screw means which are projected through the outlet of said cage section to terminate immediately adjacent the end of said independent screw means remote from said discharge opening.

6. A dewatering or like press structure, including an initial main cage section having an inlet thereto and an outlet therefrom and incorporating feed screw means for advancing a pulp slurry to move from said inlet to and through said outlet, said screw means being formed to extract fluid from the pulp slurry during its movement through said cage section, said cage section being formed to provide a drain of the extracted fluids, a discharge section in connection with and providing a continuation of said cage section to form therewith a unitary housing assembly, said discharge section providing therein a discharge passage in communication with and extending angularly across the outlet of said cage section, means defining an inlet to said discharge section connecting to said cage section to rim its outlet, said discharge section having at its remote end an opening for discharge from the terminal portion of said passage, independent feed' screw means rotatable in said pass-age, said terminal portion of said discharge passage incorporating flow restricting means, there being transfer means for pressure feeding the thickened slurry delivered from the outlet of said cage section into said discharge section in a continuous flow, said transfer means extending to a 4' point immediately adiacent said independent feed screw means for direct pickup of the material thereby and the abrupt change of its direction of flow, said independent feed screw means 'being formed and operable to apply a selected back pressure on said transfer means and further compress the materials in the thickened slurry in the process of positively moving the resultant product to and through said discharge opening, and said discharge section incorporating means for relieving pressure on the material delivered thereto, in the area of its inlet, to provide thereby that said first-mentioned screw means operate under minimal pressure without loss of operating cfficiency.

7. A dewatering or like press structure as in claim 6 characterized by said discharge section of said housing assembly having, immediately facing its inlet, means defining a relatively enlarged portion of said discharge passage formed with openings to provide both drain of fluid and pressure relief at the commencement of said discharge passage which positions directly across the outlet of said cage section.

3. In the art of pulp handling wherein the consistency of a pulp-liquid slurry is thinned for screening and cleaning and is thickened to a selected dryness preparatory to refining or storage; the improvement comprising a dew-atering apparatus adapted to be installed in the pulp processing system in advance of a refiner, a storage chest or the like for thickening purposes, said apparatus comprising a continuous housing including therein continuous helical press structure for accepting thinned pulp slurry at a relatively rapid feed rate, said housing structure including a first section having an inlet at one end and an outlet at the other end and an intermediate drain section, twin overlapping helical screw means longitudinally disposed in said first section having extensions at their outer ends extending in and beyond said outlet, means for rotating said screw means under sufiicient power to produce in conjunction with the frictional resistance of the material on said screw means a pressure at the outer end of said drain section yielding a degree of dryness which approaches but is less than the selected fin al dryness, a second section of said housing structure immediately following the first section having means defining an inlet thereto in closed communication with the outlet of said first section, secondary helical screw means in said second section positioned immediately adjacent the terminal extremities of said extensions of said twin overlapping helical screw means to receive material directly therefrom and operable on the material delivered thereto to extract further liquid therefrom, choke means at the terminal end of said second press section following said secondary helical screw means, in which choke means the material delivered from said secondary screw means forms a relatively dry plug in discharge from said apparatus, said extensions of said first-mentioned helical screw means providing for a continuing force feed of the slurry from said first section to said secondary screw means, and said second section of said housing structure having immediately adjacent said extensions of said screw means means defining drain openings, the arrangement providing that said secondary screw means produces a back pressure which is at a maximum at said extensions of said first-mentioned helical screw means and diminished in the area of said first-mentioned helical screw means inwardly therefrom, said drain means acting as valving means operating in a manner to limit the back pressure influenced by said second screw means.

9. Dewatering apparatus according to claim 8 characterized by said helical press structure being adapted to accommodate slurry thinned to a value on the order of 5% of solids and delivered at a rate in the area of 300 gallons per minute and to achieve a dryness on the order of 30% solids, said first mentioned helical screw means having controls providing that it create a pressure in the neighborhood of 25 pounuds per square inch at the outer end of the said drain section to yield a dryness of about 20% solids at that point, said valving means being designed to limit back pressure on said feed screw extensions whereby to achieve at said choke a final dryness on the order of 30% solids.

References Cited UNITED STATES PATENTS 2,249,736 7/1941 Anderson -145 X 2,331,883 10/1943 Anderson 100145 2,943,012 2/1960 Dunning et al. 100-117 X 3,003,412 10/1961 Vincent 100-117 3,067,672 12/ 1962 French. 3,070,005 12/1962 Kemp et al. 100146 PETER FELDMAN, Primary Examiner U.S. Cl. X.R. 100-146

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