US3674217A - Pulp fiberizing grinding plate - Google Patents

Abstract

A pulp fiberizing grinding plate or disc, known in the art as the ''''Asplund Defibrator,'''' employed for breaking down wood chips, or the like fibrous material into fibers for use in various pulp employing processes, such for example, as in the paper industry, or the like. The defibrator plate or disc is formed of disc segments with a grinding face having a plurality of upstanding ribs extending across the working area of the plate, with the ribs at the beginning of the working area lying at an angle of between 0* and 60* to a radius intercepting the rib at the commencement of the rib in the working area, with the rib gradually transitioning across the working area at a progressively increasing angle to the plate radius, until at the circumference, the ridge is at an angle of between 65* and 90* to the radius. The ridges of this plate face similar ridges on an opposed grinding surface, with relative movement provided for between the grinding surfaces. As a result of the angulation of the ridges or ribs, the previously encountered problems of fiber breakage, occurring on previously evolved grinding plates is eliminated, since the angulation between the relatively moving ridges minimizes the shear forces exerted on the fibers, producing instead of the conventional fiber cutting action, a compressive fiber separating pushing force.

Description

July 4, 1972 United States Patent Reinhau [57] ABSTRACT berizing grinding plate or disc, known in the art as the Asplund De [54] PULP FIBERIZING GRINDING PLATE [72] Inventor: Rolf Berti] Reinhall, 16, Killingevagen, Apulp Lidingo, 3,Sweden brator, employed for breaking down wood chips, or the like fibrous material into :bers for use in various 13 Claims, 5 Drawing Figures l PTNTl-INULv 41972 INVENTOR ROLF REINHALL MIM ATTORNEYS` PULP FIBERIZING GRINDING PLATE BACKGROUND OF THE INVENTION This invention relates to the art of fiber separation, and more particularly to an improved grinding plate for use in breaking up brous materials into their constituent fibers.

A variety of so called grinding plates or discs have been evolved for use in breaking down fibrous stock into a fibrous pulp.

These grinding plates as conventionally employed, comprise a rotating disc or plate, having a plurality of spaced ridges, moving against an opposed surface having similarly arranged ridges, with the stock fed between the relatively moved ridge surfaces so as to crush the stock into a brous pulp. The action is of a grinding nature, and it is common to refer to such discs as grinding discs or plates.

The quality of the fibrous pulp produced by any of these grinding plates is determined by an analysis of the liber length of the fibers comprising the pulp. This fiber length is dependent on nature of the stock fed to the discs, and on the nature of the grinding action.

Grinding plates generally comprise a plurality of arcuate segments arranged end-to-end around the center portion of the disc. The segments are formed with ribbed grinding faces, and the disc is mounted to move against a surface having similar ribs.

The chips of the stock to be ground are delivered to the center of the grinding disc where they are thrown outward by the centrifugal force imparted to them.

Fiber separation takes place as the steam softened chips pass between the grinding segments, thus the centrifugal force of the rotating plate carries the chips between the ridges on opposed faces, and in moving between these ridges, the chips are broken down into their fiber constituents.

On conventional grinding plates, the ridges extend substantially radially over the surface of the plate. The chips which are being moved across the working area of the plate are thus crushed between the relatively moving ridges. The relatively moving ridges simultaneously act as a pair of shears on the fibers being separated from the chips, with the result that the fibers are cut as they are separated from the chip.` 'This produces an undesirably small fiber length in the fibrous pulp.

Further problems are encountered in that the full working area of the relatively rotating grinding disc is not fully utilized, since the channels between the ridges on the grinding plates are spread out over a greater area at the periphery of the grinding plate, than at the center nearthe beginning of the working area. Thus the chips moving from the center of the disc toward the periphery, quickly fill up the channels at the beginning of the working area, while the channels at the periphery of the working area are relatively empty.

BRIEF DESCRIPTION OF INVENTION It is with the above considerations in mind, that the present improved grinding plate or disc has been evolved serving to crush the chips of fibrous material to break the chips into their fibrous constituents, with minimal cutting of the fibers, and in a fashion such that the entire working area of the grinding plate is kept filled with material being processed.

It is accordingly among the primary objects of this invention to provide an improved grinding plate segment in which the grinding action of the segment on the chips being processed serves to break down the chips into their fibrous constituents, with minimal cutting ofthe fibers.

A further object of the invention is to provide a grinding plate with a working surface configuration such that the rate of feed along the plate working surface of the chips being ground into their fibrous constituents is controlled so that the entire working surface of the plate segment is filled.

Another object of the invention is to provide a grinding plate segment with grinding ridges formed in a fashion to minimize grinding plate wear.

These and other objects of the invention which will become hereafter apparent are achieved by forming a grinding plate segment with a plurality of ridges arranged over the working surface of the segment so that at the inner end of the ridge on the working area, the ridges lie at an angle of between 0 and 60 to a radius extending from the center of the grinding plate to the point of interception of the working area, with the ridges transitioning across the working area at a gradually increasing angle to a plate radius extending from the center of rotation of the first mentioned radius so that at the leaving end of the working area, the grinding ridge lies at an aiigle of between 65 and 90 to the last mentioned radius. On the opposed plate, the ridges lie at an angle which is relatively acute to the ridges of the opposed grinding surface, with the resultant forces exerted on the chips being ground acting to push the chips from the inner to the outer end of the working area exerting a minimal cutting force on the fibers, the pushing force exerted serving to break the chip down hito its fibrous constituents. The spacing between the ridges provides channels of gradually decreasing cross section towards the periphery of the grinding disc, so that all of the channels across the working surface are substantially filled by the chips being processed.

A feature of the invention resides in the fact that the ridges or ribs which exert a pushing force on the chips being processed, not only minimize fiber damage, but reduce wear on the giinding ridges.

Another feature of the invention resides in the fact that the formation of the ridges or ribs with channels therebetween of gradually restricted cross section permits a relatively uniform continuity of out-put of the pulp from the grinding equipment.

BRIEF DESCRIPTION OF DRAWINGS The specific details of a preferred embodiment of the invention and their mode of functioning will be particularly pointed out in clear, concise, and exact terms in conjunction with the accompanying drawings wherein:

FIG. 1 is a plan view of a grinding disc segment showing the working area formed with ridges or ribs contoured in accordance with the teachings of this invention;

FIG. 2 is an enlarged cross sectional view taken on line 2-2 of FIG. 1 illustrating how the ridges are formed to permit the pulp to roll from one channel to the other;

FIG. 3 is a cross sectional view taken on line 3-3 through a dam ridge at the end of a channel;

FIG. 4 is an enlarged schematic view showing the action of the ridges on a pulp chip caught therebetween;

FIG. 5 is a schematic view showing the action of the ridges on the pulp chip of a conventional grinding disc.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now more particularly to the drawings, like numerals in the various figures will be employed to designate like parts. The grinding plate segment 10 illustrated in FIG. l, made in accordance with the teachings` of this invention, is of an arcuate configuration, conventionally formed by casting in the shape of the illustrated configuration. Thelateral edges 12 and 14 of the illustrated segment 10 lie along the radii of the grinding disc of which the illustrated segment 10 will form a part, as hereinafter described.

A plurality of spaced ridges orribs 15 are formed on the segment l0, with these ribs l5 extending from a point towards the inner edgel of the work area (closer to the lower end of the illustrated grinding segment) to a point at theperiphery 22 of the segment.

In forming the illustratively shown grinding plate segment l0 as shown in FIG. 1, the segment is fiornied with a center ofcurvature 18 about whicharcs 20 and 22 are swung defining the beginning and end respectively of theworking area 25 of the plate.

Arib arc circle 27 lying on a radius between the center ofcurvature 18, and thearc 20 defining the beginning of the working area is provided, andarcs 28 defining the center lines of the ribs are swung from thiscircle 27, at points preferably spaced along the circumference of the rib arc circle, so that as will be apparent, the arc defining each of the ribs will progressively taper towards a preceding rib arc thereby formingchannels 29 between the ridges which are of progressively decreasing cross section if the radii of the arc are equal. The number of ridges, as illustrated, gradually decrease toward the disc rim as a result of the fact that pairs of ridges merge. Thus ridge 15l merges intoridge 152, connected by connecting ridge portion 153, from which ridge 154 extends. The specific parameters of the radii may be varied. However, it is found preferable to form the rib arc circle of a radius between 50 and 90 percent of that of the radius of the circle defining the beginning of the working area.

The velocity of feed of the fibrous material is inversely proportional to the angle of inclination of the ribs so that the velocity of feed decreases as the rib angle increases. On the other hand the total area of the channels between the ribs increases towards the outer edge of the disc working surface, preferably to the second power of' the radius. Thus if the radius increases from the center by two inches the channel area increases by four inches. In the illustrated preferred embodiment, the inclination of the ribs with respect to the radii increases so that the rate of material feed decreases. The decrease in material velocity is compensated by increased channel area insuring the fact that all channels are filled throughout.

As can be seen from FIG. l, in the illustrated preferred embodiment, it is preferred that at least some of the ribs upstream of others of the ribs be provided at a greater spacing between said upstream ribs that the downstream ribs so that the upstream channel will be greater in cross section than its preceding downstream channel thereby providing for a turbulence producing pressure relief on the fiber chips being ground.

This can best be seen by considering labelledupstream channel 30 receiving the ground material fromchannels 31 and 32 (see upper left of FIG. l). Each of the ridges orribs 28, as best seen in FIG. 2 is formed with aninclined sidewall 33 terminating in arounded fillet 34 between theinclined rib sidewall 33 and the channel bottom, on the side of the rib closest to the beginning of theworking area 25. The opposite rib ofsidewall 33 is substantially perpendicular to the channel bottom.

Dam ribs orridges 37 are extended between ribs to define the ends of thechannels 29 betweenribs 15. These dam ridges, are positioned at different spaced points on the grinding plate so that the free length of adjacent channels will be different. Eachdam ridge 37, as best seen in FIG. 3 is formed with aninclined wall 38 merging into the channel bottom atrounded fillet 39 on the downstream side ofridge 37.

It is preferred that theribs 15 at the beginning of the working area be of gradually increasing height and bevelled as at 40 to form entry tips on the ribs, thereby implementing the flow of material into thechannels 29 between the ribs.

OPERATION ln use, the grinding plate segment 10 will as understood by those skilled in the art be assembled with a plurality of like segments to form a disc which is mounted in opposition to a similar disc, as set forth by way of example in U.S. Pat. No. 2,035,994 so that wood chips or the like fibrous material will be broken down into its fibrous constituents when the material moves outwardly from the center between the relatively moving discs.

A wood chip or the like fibrous material M as seen in FIG. 4 moves into theworking area 25 of FIG. l, enteringchannels 29 between the gradually increasing in height entry end of ribs l having bevelled entry tips 40 (see lower left of FIG. 1).

Once within thechannels 29, the chips M are pushed along the channel by the action of the channels on the opposed grinding disc.

As shown schematically in FIG. 4,ribs 15 exert a pushing force on chip M at an angle to the desired direction of movement of the chip in the channel which is not perpendicular to the desire direction of movement, as is illustrated in FIG. S, but is preferably at an angle of between 15 and 75 to a diameter of M perpendicular to the desired direction of movement of chip M.

Thus instead of shearing the chip fibers, as occurs in conventional radially extending grinding ribs, the action of which is illustrated in FIG. 5, the forces on chips M are resolved into a vector resultant, as shown in FIG. 4, pushing the chips along thechannels 29, simultaneously crushing the chips with minimal fiber shearing.

At the end of eachchannel 29, andl before reaching the end of the channel, the chips may roll over the rib edges up filleted inclined walls, thus producing desired crushing without fiber cutting.

Agitation of the ground chips, implementing turbulence and fiber separation is provided by feeding the chips from a constrained portion of one channel to a wider channel section.

It is thus seen that an improved grinding plate segment has been provided implementing the fiber separation of fibrous masses, with minimal cutting of the fibers.

What is claimed is:

1. A grinding plate segment comprising: a plate ember having a grinding face on one surface thereof; a plurality of spaced arcuate ribs on said face with material flow channels between said ribs, said ribs extending across the working area of the grinding face, at a progressively increasing angle as the distance from the working area increases, said angle being between 0 and 60 to a radius of the plate intercepting the end of the rib at its beginning in the plate working area, and at an angle of between 65 and 90 to a radius intercepting the end of the rib at the periphery of the working area of said plate member.

2. A grinding plate segment as in claim l in which each of said ribs is formed with a rounded fillet between the rib sidewall and the channel bottom on the side of said rib closest to the beginning of the working area of said grinding plate.

3. A grinding plate segment as in claim 2 in which the opposite side of said ribs extends substantially perpendicular to the channel bottom.

4. A grinding plate segment comprising: a plate member having a grinding face on one surface thereof; a plurality of spaced ribs on said face with material flow channels between said ribs, said ribs extending across the working area of the grinding face, and lying at an angle of between 0 and 60 to a radius of the plate intercepting the end of the rib at its beginning in the plate working area, and at an angle of between 65 and 90 to a radius intercepting the end of the rib at the periphery of the working area of said plate member and plurality of dam ridges are fonned at spaced intervals on said plate member between two adjacent ribs.

5. A grinding plate segment as in claim 4 in which adjacent channels have dam ridges at different spaced points so that the free length of adjacent channels will be different.

6. A grinding plate segment as in claim 4 in which said dam ridges are formed with a rounded fillet formed on the downstream side of said ridge between the ridge and the channel bottom.

7. A grinding plate segment comprising: a plate member having a grinding face on one surface thereof; a plurality of spaced ribs on said face with material flow channels between said ribs, said ribs extending across the working area of the grinding face, and lying at an angle of between 0 and 60j to the radius of the plate intercepting the end of the rib at its beginning in the plate working area, and at an angle of between 65 and 90 to a radius intercepting the end of the rib at the periphery of the working area of said plate member, at least one of the channels of the segment being formed with a spacing between the ribs defining said channel of a gradually approaching orientation in a direction towards the outer edge of said segment.

8. A grinding plate segment comprising: a plate member having a grinding face on one surface thereof; a plurality of spaced ribs on said face with material flow channels between said ribs, said ribs extending across the working area of the grinding face, and lying at an angle of between 0 and 60 to a radius of the plate intercepting the end of the rib at its beginning in the plate working area, and at an angle of between 65 and 90 to a radius intercepting the end of the rib at the periphery of the working area of said plate member, some of the channels downstream of other of said channels in the direction of the flow of material over said segment having greater cross-section than the preceding channels.

9. A grinding plate segment comprising: a plate member having a grinding face on one surface thereof; a plurality of spaced ribs on said face with material flow channels between said ribs, said ribs extending across the working area of the grinding face, and lying at an angle of between 0 and 60 to a radius of the plate intercepting the end of the rib at its beginning in the plate working area, and at an angle of between 65 and 90 to a radius intercepting the end of the rib at the periphery of the working area of said plate member, at least one of said ribs being formed with entry tips cut at an angle to the direction of flow of material in the channels formed by said ribs.

10. A grinding plate segment comprising: a plate member having a grinding face on one surface thereof; a plurality of spaced ribs on said face with material flow channels between said ribs, said ribs extending across the working area of the grinding face, and lying at an angle of between 0 and 60 to a radius of the plate intercepting the end of the rib at its beginning in the plate working area, and at an angle of between 65 and 90 to a radius intercepting the end of the rib at the periphery of the working area of said plate member, at least some of said ribs being formed of gradually increasing height at their ends adjacent the beginning of the working area.

g 1 l. A method of breaking fibrous material into its fiber constituents comprising the steps of moving the fibrous material along a rigid surface; exerting a pushing force on the brous material at an angle to the desired direction of movement of the fibrous material having a vector resultant in the desired direction of movement, said pushing force being exerted at an angle of between 15 and 75 to a diameter perpendicular to the desired direction of movement of said fibrous material, thereby minimizing the shear force exerted on the fibers of said fibrous material.

12. A method as in claim 11 in which the pushing force on said fibrous material is periodically relieved as the fibrous material is moved over the rigid surface, thus disturbing any equilibrium of said material, and implementing its break down.

13. A grinding disc having a grinding surface formed by spaced arcuate ribs and channels intermediate said ribs, said ribs extending from the beginning of a working area towards the center of said disc at an angle of between 0 and 60 to a radius of said disc and increasing progressively as the distance from the center increases towards the periphery of said disc where said ribs lie at an angle of between 65 and 90 to the radius of said disc, the rate of increase of the angle of said ribs with respect to the disc radius being such as to correspond to the decrease in the rate of feed of material and to the increase in channel area to maintain said channels filled with brous material throughout.

Claims (12)

1. 2. A grinding plate segment as in claim 1 in which each oF said ribs is formed with a rounded fillet between the rib sidewall and the channel bottom on the side of said rib closest to the beginning of the working area of said grinding plate.
2. 3. A grinding plate segment as in claim 2 in which the opposite side of said ribs extends substantially perpendicular to the channel bottom.
3. 4. A grinding plate segment comprising: a plate member having a grinding face on one surface thereof; a plurality of spaced ribs on said face with material flow channels between said ribs, said ribs extending across the working area of the grinding face, and lying at an angle of between 0* and 60* to a radius of the plate intercepting the end of the rib at its beginning in the plate working area, and at an angle of between 65* and 90* to a radius intercepting the end of the rib at the periphery of the working area of said plate member and plurality of dam ridges are formed at spaced intervals on said plate member between two adjacent ribs.
4. 5. A grinding plate segment as in claim 4 in which adjacent channels have dam ridges at different spaced points so that the free length of adjacent channels will be different.
5. 6. A grinding plate segment as in claim 4 in which said dam ridges are formed with a rounded fillet formed on the downstream side of said ridge between the ridge and the channel bottom.
6. 7. A grinding plate segment comprising: a plate member having a grinding face on one surface thereof; a plurality of spaced ribs on said face with material flow channels between said ribs, said ribs extending across the working area of the grinding face, and lying at an angle of between 0* and 60*j to the radius of the plate intercepting the end of the rib at its beginning in the plate working area, and at an angle of between 65* and 90* to a radius intercepting the end of the rib at the periphery of the working area of said plate member, at least one of the channels of the segment being formed with a spacing between the ribs defining said channel of a gradually approaching orientation in a direction towards the outer edge of said segment.
7. 8. A grinding plate segment comprising: a plate member having a grinding face on one surface thereof; a plurality of spaced ribs on said face with material flow channels between said ribs, said ribs extending across the working area of the grinding face, and lying at an angle of between 0* and 60* to a radius of the plate intercepting the end of the rib at its beginning in the plate working area, and at an angle of between 65* and 90* to a radius intercepting the end of the rib at the periphery of the working area of said plate member, some of the channels downstream of other of said channels in the direction of the flow of material over said segment having greater cross-section than the preceding channels.
8. 9. A grinding plate segment comprising: a plate member having a grinding face on one surface thereof; a plurality of spaced ribs on said face with material flow channels between said ribs, said ribs extending across the working area of the grinding face, and lying at an angle of between 0* and 60* to a radius of the plate intercepting the end of the rib at its beginning in the plate working area, and at an angle of between 65* and 90* to a radius intercepting the end of the rib at the periphery of the working area of said plate member, at least one of said ribs being formed with entry tips cut at an angle to the direction of flow of material in the channels formed by said ribs.
9. 10. A grinding plate segment comprising: a plate member having a grinding face on one surface thereof; a plurality of spaced ribs on said face with material flow channels between said ribs, said ribs extending across the working area of the grinding face, and lying at an angle of between 0* and 60* to a radius of the plate intercepting the end of the rib at its beginning in the plate working area, and at an angle of between 65* and 90* to a radius intercepting the end of the rib at the periphery of the working area of said plate member, at least some of said ribs being formed of gradually increasing height at their ends adjacent the beginning of the working area.
10. 11. A method of breaking fibrous material into its fiber constituents comprising the steps of moving the fibrous material along a rigid surface; exerting a pushing force on the fibrous material at an angle to the desired direction of movement of the fibrous material having a vector resultant in the desired direction of movement, said pushing force being exerted at an angle of between 15* and 75* to a diameter perpendicular to the desired direction of movement of said fibrous material, thereby minimizing the shear force exerted on the fibers of said fibrous material.
11. 12. A method as in claim 11 in which the pushing force on said fibrous material is periodically relieved as the fibrous material is moved over the rigid surface, thus disturbing any equilibrium of said material, and implementing its break down.
12. 13. A grinding disc having a grinding surface formed by spaced arcuate ribs and channels intermediate said ribs, said ribs extending from the beginning of a working area towards the center of said disc at an angle of between 0* and 60* to a radius of said disc and increasing progressively as the distance from the center increases towards the periphery of said disc where said ribs lie at an angle of between 65* and 90* to the radius of said disc, the rate of increase of the angle of said ribs with respect to the disc radius being such as to correspond to the decrease in the rate of feed of material and to the increase in channel area to maintain said channels filled with fibrous material throughout.

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