Note: Descriptions are shown in the official language in which they were submitted.
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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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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
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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.
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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
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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.
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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
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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.
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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.
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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).
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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.
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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
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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
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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.
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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
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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.
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