CA1226207A - Methods and apparatus for longitudinally slitting plant material - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A slitter cuts flattened pieces of fibrous plant material into longitudinal strips. The slitter comprises a pair of opposed rotary members each having a plurality of annular cutting teeth. Each cutting tooth comprises an outer annular cutting edge, a radial rear race, and a non-radial front face. The cutting teeth of the two rotary members overlap radially to engage opposite sides of a plant piece and completely cut through the plant piece and slit same into strips. The teeth define cells in which the strips are rotated while being fed. front faces of the cell are arranged opposite each other and spaced apart at the point of maximum overlap to define a cell width corresponding to the thickness of the plant piece to grip the sides of the respective strip and positively advance and discharge same.
In a modified embodiment, the teeth include replaceable cutting inserts which are removably attached to base members and extend radially there beyond. This arrangement increases the amount of cutter overlap without reducing the size of the cells. The inserts are attached to the base members by solder and are removed therefrom by melting the solder.

Description

~Z~6207 I`

.' BACKGROUND AND OBJECTS OF THE Intention ` The present invention relates to material shredding and, in particular to the slitting of fibrous plant material into longitudinal strips.
Apparatus and techniques are in practice in which sugar cane stalks are cut transversely into short billets and then fed lengthwise through a high-speed separator. In the separator the billets are split longitudinally in half and flattened. The flattened stalk halves are then milled such that the sugar-containing with component of each stalk half is removed from the fibrous rind component of the stalk.
The rind sections are then discharged from the separator in essentially an undamaged condition. This technique is described in more detail in US. Patent No. 4,312,677 issued to Sydney E. Tilby and Brando Vocalic on January 26, 1982.
The fibers of the rind sections are useful in the fabrication of various products, especially boards, by a method explained, for example, in US. Patent No. 4,212,616 , issued to Sydney E. Tilby on July 15, 1980. For use in such a technique it is desirable that the rind sections be long-tudinally separated into more narrow fiber bundles.

A convenient and efficient manner of slitting the rind segments is to position a shredder or slitter at the outlet of the separator which slits the rind segments as they are disk charged see the above-mentio~ed US. Patent 4,312,677), since the segments are already longitudinally oriented and in motion.

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lZ~62~7 A serious drawback to such a positioning of the shredder is the fact that the shredder must be capable of handling a large volume of rapidly moving rind segments, i.e., the rind segments may ye discharged at a speed of about 3 meters/sec. Conventional stalk cutters are not capable of shredding stalks longitudinally at such speeds.
A prior art slitter depicted in Figures 1 and 2, includes a pair of opposed, identical roll units 10, lo rotating about spaced parallel axes 12, 12, The not l units comprises a plurality of thin toothed disks 14, AYE spaced apart by smaller-diameter spacer disks 16, AYE. The toothed disks of one roll unit are offset axially relative to those of the other roll unit. The distance between the axes 12, AYE is less than twice the radius of the cutter disks, so that the toothed disks of the roll units intermesh, with the toothed disks of each roll unit opposing a spacer disk of the other roll unit. Accordingly, as a section of stalk rind B is fed longitudinally into the nip 18 formed by the toothed disks 14, AYE, the adjacent toothed disks overlap radially to shear through the billet and separate the latter into longitudinal strips BY. us the toothed disks continue to rotate, the strips BY fall from between the roll units. Stationary fingers or combs 19, lea are disposed around the spacer disks 16, AYE
to prevent plant fibers from wrapping around the spacer disks.
Among the disadvantages of such a slitter arrangement is the inability to cut and discharge the strips at a sufficiently high rate to keep up with the rate of discharge of rind from the separator. In addition, the fingers 19, lea, being ~ZZ62~7 stationary, do not promote the egress of juice, pith, etc., from the unit which can thus create resistance to rotation, thereby reducing speed and increasing power requirements.
It has also been heretofore proposed to cut articles by means of inter meshing cutter disks having beveled edges, as demonstrated by the disclosures of US. Patent 1,546,018 issued to Mollenberg et at on July 14, 1925, and US. Patent 1,731,967 issued to Antonsen on October 15, 1929. In the Mollenberg et at patent, stalks are chopped transversely (i.e., perpendicular to the individual fibers). Once the stalk has been completely severed within the cutting nip, there does not exist enough surface contact between the disks and the cut pieces of stalk to induce a sufficiently high discharge speed of the cut stalk pieces to satisfy the needs of a high-speed separator. In the Antonsen patent, paper is fed longitudinally into a shredder, but the principles under which paper shredders operate would not enable a stalk shredder to be constructed which is capable of cutting high volumes of stalks traveling at high speeds.
Accordingly, it is an object of the present invent lion to minimize or obviate problems of the above-discussed sort.
Another object of the invention is to provide a speed stalk shredder capable of slitting plant stalks longitudinally at high speed.
A further object is to provide methods and apparatus for simultaneously effecting a slitting and high-speed feeding of plant stalks.

~Z~6;~1~7 An additional object is to provide a slitter capable of slitting stalks at speeds of about 3m/sec minimum.
Another object is to provide a slitter in which the cutting edges are easily and inexpensively renewed.
An additional object is to provide a novel method of bonding a cutting insert to a base member.

SUMMARY OF THE INVENTION
These objects are achieved by the present invention which involves a slitter for slitting flattened pieces of fibrous plant material into longitudinal strips. The slitter comprises a pair of opposed rotary members driven about horn-zontally spaced, substantially horizontally parallel axes.
Each rotary member comprises a plurality of longitudinally spaced annular cutting teeth. Each cutting tooth comprises an outer annular cutting edge, a generally radial rear face, and a non-radial front face. The rear and front faces converge in an outward direction. The rotary members are spaced apart such that the cutting teeth of both rotary members overlap radially to engage opposite sides of a plant piece and completely cut through the plant piece and slit same into strips which are rotated within a cell bordered by a front face of the other rotary member. The front faces of the cell are arranged opposite each other and are spaced apart at the point of maximum overlap of the rotary members to define a cell width corresponding substantially to the thickness of ~2Z6Z~7 the plant piece. The Ryan faces grip the respective strip along its thickness-defining sides and positively advance same.
Such an arrangement enables the plant pieces to be cut and discharged at high throughput speeds.
Preferably, each cell has a length extending perpendicular to the width. The cell length is longer than the spacing between adjacent cutting edges of a given rotary member. This assures that gaps will be formed at opposite edges of the strips in the cells to facilitate the discharge Of juices from the rotary members. If such juices were otherwise allowed to build-up, considerable resistance to rotation could result.
In a modified embodiment of the invention, the cutter members comprise a series of longitudinally aligned disks.
Each disk includes an annular tooth comprising a replaceable cutting insert mounted on a base portion of the disk. The insert projects radially beyond a front face of the base member to maximize the extent of overlap between opposing discs without reducing the cell size. Preferably, the inserts are stamped from spring steel ribbon and are mounted to the base portion by solder which can be melted to accommodate replacement of worn inserts.
. The present invention also involves steps performed by the above-described mechanism.

~Z~62~7 THE DRAWING

The objects and advantages of the invention will become apparent from the following detailed description of preferred embodiments thereof 7 in connection with the accompanying drawings in which like numerals designate like elements, and in which:
Figure 1 is a cross-sectional view taken along line 1-1 of Figure 2 depicting a prior art shredder in the region of disk overlap, as a plant piece is being fed through the shredder;
Figure 2 is a vertical sectional view through the prior art shredder depicted in Figure 19 as a piece of plant material is being fed vertically there through;
Figure 3 is a plan view of an end portion of a slitter according to the present invention;
Figure 4 is a side elevation Al view of the slitter of Figure 3 as a piece of plant material approaches the nip zone;
Figure 5 is an enlarged view of the nip zone of the slitter of Figure 3, depicting the various positions in which the leading end of a piece of plant material assumes as it travels through the slitter;
Figure 6 is a horizontal sectional view taken along line Ç-6 of Figure 5 depicting the relative orientation of the plant material and cutter teeth as the plant material enters the nip zone;
Figure 7 is a horizontal sectional view taken along line 7-7 of Figure 5 depicting the relative orientation of ~Z6;~7 the plant piece and the cutter teeth at the instant when the cutter teeth have completely severed through the plant piece;
Figure 8 is a horizontal sectional view taken along - line 8-8 of Figure 5 depicting the relative rotation of the plant strips and cutter teeth at the point of maximum overlap of the cutter teeth, after the plant strips have been turned within the cells and are being positively gripped by the front faces of the cutter teeth;
Figure 9 is a horizontal sectional view taken along line 9-9 of Figure 5, depicting the plant strips being disk charged from the slitter;
Figure 10 is a horizontal sectional view taken through a portion of the slitter, depicting an initial step to be taken in a tooth-sharpening operation;
Figure 11 is a view similar to Figure 10 depicting a subsequent step taken during the tooth-sharpening opera-lion;
Figure 12 is a view similar to Figure 8 in the absence of the plant strips;
Figure 13 is an enlarged view of the nip of a modified slitter according to the present invention in which the teeth include replaceable cutting inserts;
Figure 14 is a side elevation Al view of a cutting insert; and Figure 15 is an exploded schematic view of a press in which a cutting insert is mounted on a base member.

~Z~Z~7 DETAILED DESCRIPTION OF PREFERRED
EMBODIMENTS OF THE INVENTION

A stalk slitter according to the present invention is depicted in Figures 3 to 11 and comprises a pair of oppositely spaced identical rotary cutter members in the form of rolls 20, AYE driven about horizontally spaced horizontal axes 21, AYE. A suitable drive mechanism (not shown) is provided for rotating the rolls at a synchronized high speed.
Projecting radially from the rolls are a plurality of annular cutter teeth 22, AYE spaced along the axis of the respective roll. The teeth are integral with the roll structure. Alternatively, the cutting members may comprise a series of longitudinally aligned disks each having a tooth.
Each tooth is beveled along its periphery to form a radial rear face 24, AYE and a non-radial front face 26, AYE.
Those front and rear faces converge outwardly to form annular cutting edges 28, AYE. The rolls 20, AYE are spaced apart by an amount less than the diameter of a cutting edge, so that the teeth 22, AYE overlap radially, with the radial rear faces 24, AYE of the teeth of each roll contacting or substantially contacting the rear faces of the teeth of the other roll in the overlap region.
The rolls 20, AYE thus form a nip zone 30 within which the rind pieces B, traveling downwardly in the direct lion of their length (i.e., traveling parallel to the orientation of the individual fibers), are grasped, fed, and cut.

~z26Z(~7 As discussed earlier, the rind pieces B each comprise a flattened, longitudinally halved stalk billet, with the pith and possibly the epidermis (outer skin) removed. The rind piece B includes spaced side surfaces 32, 34 which define the thickness of the rind piece.
Figure 6 depicts a rind piece B as it enters the nip 30. The illustration is from the viewpoint of an observer standing above the rolls and looking down into the nip; the rind piece travels away from the observer and into the plane of the paper. In Figure 7, the cutting teeth 22, AYE have cut through the leading end of the rind, i.e., cooperating pairs of opposing cutting edges 28, AYE
have "met" half-way through the rind piece B. The rind piece is thus beginning to be slit into a series of thin lengthwise strips BY of fiber bundles. Each strip BY is disposed within a cell 36 defined by two teeth of each roll, the cell being bordered by the radial rear faces 24, AYE and the non-radial front faces 26, AYE of those teeth.
As the rind piece B continues its downward travel toward a center plane 37 containing both roller axes 21, AYE, the opposing teeth 22, AYE overlap radially to a progressively greater extent. In so doing, the non-radial front faces 26, AYE of each cell 36 impose a force couple 38 upon the respect live strip AL in a manner tending to rotate the strip within the cell about an axis parallel to the direction of strip travel (i.e., parallel to the individual fibers of the strip).

~2Z~Z~

By the time the leading ends of the strips BY
reach the center plane 37 (the point of maximum overlap of the teeth), such leading ends will have been turned by an angle corresponding to the angle of inclination 40 of the front faces 26, AYE (Fig. 8).
In accordance with the present invention, the minimum width 42 of the cell defined by the distance between the opposing front faces 26, AYE of a given cell 36 at the plane 37 is sized to assure that those front faces 26, AYE contact the side surfaces 32, 34 of the respective strip AL. That is, such distance 42 corresponds substantially to the thickness of the rind piece. This can be achieved by presetting such distance 42 at the lower end of the range of rind thicknesses was determined by measuring the thickness of rind pieces discharged from a known separator for example).
This assures that the side surfaces 32, 34 of virtually all of the rind pieces will be contacted at the plane 37; the thicker pieces may even be somewhat compressed between the front faces.
Since each strip BY is thus positively gripped between the front faces 26, AYE of both driven rolls 20, AYE, the strip is positively driven toward the do charge of the nip by the rolls with minimum slippage occurring between the strips and the rolls. This enables the strips to be rapidly advanced through the nip 30 so that slitting can be achieved at high speeds equaling the output rate of a stalk separator.

~Z~6Z~7 The length 44 of a cell extending perpendicularly to the width thereof defined by the front faces 26, AYE is preferably longer than the distance 46 separating adjacent cutting edges 28 (or AYE) of a given roll. This assures that gaps I will remain at opposite sides of each strip to allow for the escape of juice which otherwise could retard the speed of the strips and rolls.
If desired, scrapers 50 (Fig. 4) may be arranged to remove pith, juice, and other substances from the teeth of the rollers.
One advantage of the roll arrangement described thus far is the ability to conveniently resharpen the cutting edges 28, AYE. When those edges become dulled, the rolls 20, AYE are mutually separated in the direction of their axes as depicted in Figure 10. The rolls are then removed radially together until the cutting edges of each roll extend practically to the roots of the cutting teeth of the other roll. Lapping compound is applied to the teeth, and the rolls 20, AYE are moved axially to inter engage the radial rear faces 24, AYE as depicted in Figure 11. By then rotating the rolls while pressing the radial rear faces against each other, the cutting edges 28, AYE will be resharpened. This procedure may also be employed to fit the teeth of a new roll to those of an old one.
IN OPERATION, the rolls 20, AYE are rotated about their horizontal axes so that the cutter teeth 22, AYE mutually overlap in a radial direction. Plant pieces B, such as pieces ~2Z6Z~7 of rind, are fed downwardly, while oriented in their lengthwise direction, into the nip 30 defined by the rolls.
The meshing cutter teeth feed the pieces B downwardly while slitting them into lengthwise strips BY confined to respect live cells 36. The front faces 26, AYE of the teeth 22, AYE
- act upon the strips and rotate the latter such that the sides 32, 34 of the strips become oriented parallel to the front faces 26, AYE and are positively engaged by the latter.

Juices or pith material are discharged from the cells 36 via the spaces 48. Overall slippage between the strips and the rolls is minimized, enabling the rolls to accelerate and discharge the strips at high speed.
It will be appreciated, then, that the slitter is able to slit and discharge the plant pieces at high speed.
Such a slitter is highly suited for use with a high speed, high volume stalk separator of the type conventionally employed to separate the components of sugar cane stalks.
The cutting edges can be easily reground through the cooperation of the cutting teeth themselves.
An even more preferred embodiment of the invention is depicted in Figures 13 to 15. In this embodiment, each rotary cutter member 20', AYE' comprises a stack of disks 60, with the teeth thereof comprising a composite structure.
That is, each disk includes a base member 62 and a ring-shaped cutting insert 64 secured thereto.
The base members 62 each include a front face I
which is similar to the front face 26 described in connection lZ26Z~7~

with the earlier described embodiment The inserts 64 are stamped from a thin ribbon of spring steel of, for example, inch thickness, and are attached to the base members in any suitable fashion. The attachment is effected in such manner that a peripheral cutting edge 68 of the insert is spaced radially outwardly of the outer peripheral edge 70 of the front face 65 of the associated base member 62 by a selected distance. Each insert 64 also defines a radial rear face 67.
the peripheral edge 68 of the insert can be flat or beveled, as desired, and may include notches 69 at circumferential spaced intervals. These notches 69 define teeth which positively grip and feed the incoming stalks.
The rotary members 20', AYE' are arranged such that the inserts overlap radially. It will be appreciated that since the cutting edge of the insert is spaced radially out-warmly of the outer periphery of the front face 65, there will occur a greater amount of radial overlap without an appreciable diminishing of the area of the cells. Thus, the cutting effectiveness is increased while providing for sufficient cell area to grip the strips and conduct away juices and other plant components.
It is desirable that the base members 62 overlap to some extent to reinforce the inserts.
Since the inserts I are removable from the base members 62, they can be replaced when worn. This method of renewing the cutting edges is much less expensive than the efforts required to sharpen the earlier described edges 28.

, ~_~. ,_._.__.. _ .. _ ~2Z6Z(~7 The inserts 64 and base members 62 can be provided with slots 72 which receive keys of a mandrel upon which the disks 60 are mounted so that the inserts and base members are subjected to equal drive torques.
- Although many suitable techniques for removably securing the inserts I to the base members 62 will be readily apparent to those skilled in the art, one preferred technique will now be described in detail with reference to Figure 15. After being stamped-out by means ox a precision die, the thus-formed insert 64 is plated on one or both sides with a flash coating of copper by a conventional electrolytic process. A base member 62 is also plated with a flash coating of copper in similar fashion. The base member 62 can be formed of any rigid metal which is capable of being copper plated.
One side 74 of either the base member or insert, is then "tinned" with a finite thickness of ordinary lead/tin solder.
The insert and base member are then centered upon a lower, stationary platen 80, with the tinned side of the insert in contact with the base member. A movable upper platen 82 is lowered to press the insert and base member together. The insert and base member are heated sufficiently to raise the solder temperature jllst above the melting temperature for the particular solder being employed.
Such a temperature is far below any temperature which would affect the temper in the insert or base member. Heating can ~6Z~7 be achieved in any suitable manner, as by employing platens which conventionally include electrical heating elements or heated fluid conducting passages, along with suitably heat sensing probes.
Upon cooling, the solder hardens and forms a firm bond between the base member and insert. Such a bonding is advantageous in that it prevents stalk fibers or pith from building-up between the insert and base member as might occur if mechanical fasteners were employed to attach the insert and base member together.
To remove a worn insert 64 from its base member, the disk 60 is installed between the platens I I and is heated sufficiently to raise the solder temperature above its melting point. The insert can then be removed before the solder has an opportunity to cool and reharden. The base member can be reused, and the insert thrown away.
Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, modifications, substitutions, and deletions, not specifically described, may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A plant stalk slitter for slitting flattened pieces of fibrous plant material into longitudinal strips, comprising a pair of opposed rotary members driven about horizontally spaced, substantially horizontally parallel axis, each rotary member having a plurality of longitudinally spaced annular cutting teeth, each cutting tooth comprising an outer annular cutting edge, a generally radial rear face and a non-radial front face which faces converge in an out-ward direction, said rotary members being spaced apart such that said cutting teeth of both rotary members overlap radially to engage opposite sides of a plant piece and completely cut through and slit same into strips which become rotated within cells defined by a front face and rear face of one rotary member and a front face and rear face of the other rotary member, said front faces of each cell being arranged opposite one another and spaced apart at the other point of maximum overlap of said rotary members to define a cell width corresponding substantially to the thickness of the plant piece to grip the respective strip along its thickness-defining sides and positively advance the strip.

2. A slitter according to claim 1, wherein the radial rear faces of one rotary member engage respective radial rear faces of the other rotary member within the overlapping region of said rotary members.

3. A slitter according to claim 1, wherein each cell has a length extending perpendicular to said width, said length being longer than the spacing between adjacent cutting edges of a given rotary member.

4. A slitter according to claim 1, wherein said cutting edge is defined by the intersection of said radial and non-radial faces.

5. slitter according to claim 1, wherein said rotary members each comprise a plurality of longitudinally aligned disks, each disk comprising a base member and a replaceable cutting insert removably mounted on said base member, said front face being formed on said base member, said generally radial face and said cutting edge being formed on said insert, said cutting edge being spaced radially out-warmly of the outer periphery of said front face.

6. A slitter according to claim 5, wherein said base members of one rotary member overlap radially with the base members of the other rotary member at the point of maximum overlap of said rotary members.

7. A slitter according to claim 5, wherein each insert is removably mounted on its respective base member by solder, said insert being removable upon heating of the solder to its melting point.

8. A slitter according to claim 5, wherein said insert is formed from spring steel ribbon.

9. A plant stalk slitter for slitting flattened pieces of fibrous plant material into longitudinal strips, comprising a pair of opposed rotary members rotatably driven about horizontally spaced, substantially horizontally parallel axes, each rotary member including a plurality of longitudinally aligned annular disks, each disk comprising a base member and a ring-shaped cutting insert removably attached thereto, each base member including a non-radial front face, said insert being thinner than said base member and having a generally radial face, and an outer cutting edge spaced radially out-wardly of the outer periphery of said front face, said rotary members being spaced apart to position said inserts in radially overlapping relationship such that said inserts and front faces of both rotary members engage opposite sides of a plant piece and cut completely therethrough to slit same into strips which become rotated within cells defined by mutually opposing radial faces and front faces of said rotary members, said front faces of each cell being arranged opposite one another and spaced apart at the point of maximum overlap of said rotary members to define a cell width corresponding substan-tially to the thickness of the plant piece to grip the respective strip along its thickness-defining sides and positively advance the strip.

10. A slitter according to claim 9, wherein said inserts are formed of spring steel ribbon.

11. A slitter according to claim 9, wherein said inserts include circumferential spaced notches along said cutting edge.

12. A slitter according to claim 9, wherein said insert is bonded to its associated base member by an inter-mediate bonding layer which is meltable to permit removal of said insert.

13. A method of slitting pieces of fibrous plant material into longitudinal strips, said method comprising the steps of:
rotating a pair of opposed rotary members about horizontally spaced, horizontally parallel axes so that axially spaced cutter teeth on one rotary member overlap radially with axially spaced cutter teeth on the other rotary member, each cutter tooth including an outer annular cutting edge, a radial rear face and a non-radial front face, which faces converge outwardly, the cutting teeth of said rotary members cooperating to form a plurality of axially spaced cells along the region of overlap, each cell defined by a front and rear face of one rotary member and a front and rear face of the other rotary member, feeding said plant pieces lengthwise into said overlap region so that said plant pieces are severed into length-wise strips by cooperating pairs of said cutting edges, with each strip entering a respective cell, said strips being caused to turn in their respective cells by said front faces so that the sides of each strip become oriented parallel to said front faces and are post-lively engaged and advanced thereby.