Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FIELD OF TE~E INVENTION
The present invention relates to a chipper. More
specifically the present invention relates to a chipper for
processing whole trees and simultaneously separating debris
from the chips.
BACKGROUND OF THE INVENTION
Chips from whole trees or similar material provides
an inexpensive source of wood and many pulp mills are now
using varying proportions of these chips together with the
regular chips, However, chips from whole trees generally
contain a significant amount of long twigs or branch stems
that cause costly handling problems, for example, hang-ups
in chip bins and metering valves etc. and use of these
chips is restricted. The industry in the near future may
be forced by government regulations to further utilization
~ of the cut tree and whole tree chipping may be more
- widespread.
Convential disc chippers including those used to
chip whole trees include a housing with a disc rotably mounted
therein and provided with slots therethrough and knives.
The cut chips pass through the slots into a chamber and are
ejected from the chamber by suitable vanes projecting from
the rear face of the disc. Twigs or branch stems are not
easily cut by the knives and simply stay on the front face
` of the disc or sometimes progress to the back face of the
disc either by passing through the chip slot or around the
periphery of the disc and are thrown out the chipper spout
mixed with the cut chipso No simple and efficient way of
separating these twigs and branch stems and generally debris
associated with chipping whole tree~ has been devised to
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date.
It has been proposed to divide the chipper housing
into two compartments one of which is an involute and forms a
fan to provide more air for conveying the chips as taught, for
example, in Canadian patent 754,372 issued March 14, 19~7 to
Eklund, however, this device does not separate debris from
chips.
It has also been proposed to separate dirt and
loose bark in a drum chipper designed to chip short length
large diameter logs. In this chipper the short log lengths
are fed radially (the longitudinal axis of the log and drum
are aligned) and the knives cut substantially parallel to the
grain to form chips which pass into the drum. This device is
unsuitable for whole tree chipping.
BRIEF DESCRIPTION OF THE INVENTION
The present invention relates to a method for pro-
ducing from whole trees while simultaneously separating debris
including twigs and branches therefrom, comprising;
longitudinally feeding whole tree sections with
integral branches and twigs through an infeed spout into a
disc type chipper having a substantially radial cutting face
separating a debris chamber from a chip space located behind
said cutting face, the clearance between said cutting face and
said infeed spout providing a passage into said front chamber;
cutting the major part of said tree sections into
chips while severing branches and twigs therefrom by the
action of knives on said cutting face cooperating with an anvil
at the end of said infeed spout adjacent said face, at least
some of said branches and twigs remaining unchipped;
passing said chips into said chip space;
maintaining a clearance between cutting edges on said
knives and said anvil of at least 0.1 inches;
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moving at least some of said unchipped branches and
twigs into a position to pass through said passage into said
front chamber;
passing said unchipped branches and twigs together
with other of said debris into said front chamber;
centrifugally moving said debris radially outward
along said cutting face;
positively ejecting said debris out of said debris
ehamber through a first tangential chipper outlet leading from
said debris chamber; and
positively ejecting said chips from said chip space
through a second tangential chipper outlet, said second tangential
chipper outlet communicating with said chip spaee, whereby said
ehips and said debris are separated in said chipper and are
separately positively ejected from said chipper.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features, objects and advantages will be
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evident from the following detailed description from the
preferred embodiments of the present invention taken in con-
junction with the accompanying drawings in which:
Figure l is a schematic section along the lines l-l
of Figure 2.
Figure 2 is a schematic section along the lines 2-2
of Figure l.
Figure 3 is a view similar to Figure 2 but illus-
trating a modification of the present invention.
Figure 4 is a schematic front view with parts omitted
for clarity of the figure 3 modification of the present inven-
tion.
Figure 5 is a section along the line 5-5 of Figure 4.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As saen in Figures l and 2 the chipper 10 is formed
by a housing 12 having a front wall 14, a rear wall 16 and a
circumferential wall 18 enclosing a chipper disc r70 which is
mounted to rotate with a driven shaft 22. The disc 20 is
provided with slots 23 immediately followed by cutting knives
schematically illustrated at 24 on the substantially radial
front cutting face 25 of the disc 20~ Paddles 26 are
mounted on rear face 28 adjacent the periphery of disc 20.
A suitable wood feed inlet into the housing 12 is indicated
at 3Q. The wood is advanced substantially axially (along its
longitudinal axis) into the chipper.
The chipper is divided by the disc 20 and in the
illustrated arrangement by a annular partition 32, into a rear
chamber 34 which receives the chips that pass through slots
23 preceding each of the knives 24 and a front chamber 36
which receives the small parts of the tree that are not chipped
and can fit between the disc 20 and the adjacent end of the
infeed spout 30, i.e. leaves, twigs, branches, etc. (debris)
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which are not cut and forced to pass through the slots 23
to the rear chamber 34. Separate outlets 38 and 40 are
provided from the respective chambers 34 and 36.
Suitable paddles schematically illustrated at 42
are preferably provided on the front face of the disc 20
adjacent the periphery thereof to ensure that the front
chamber 36 remains clear.
The embodiment of Figures 1 and 2 operates as
follows:
Whole trees including the bole and top section with
branches thereon to be chipped are fed substantially axially
via the inlet or feed ~pout 30 against the front face of
the disc 20 and are cut by the knives 24. The chips so pro-
duced pass through slots 23 into the rear chamber 34 and
are swept therefrom via the paddles 26O Twigs~ leaves, etc~
(debris) ~hat do not pass through the disc 20 are pushed or
pulled into the front chamber 36 as or after they are se-
vered from the tree by the knife 24. This debris which
enters the front chamber 36 is moved along the face 25 of the
disc 20 by centrifugal force and is swept out of the chamber
36 via the paddles or the like 42 through debris outlet 40.
It will be noted that in Figure 1 separate outlets
38 and 40 for the chips and twigs etc. (debris) respectively
are shown exiting along the same tangential path but as indi-
cated by the dotted lines at 44 in Figure 1 ou~let 40 may be
in any circumferential position relative to the outlet 38.
The embodiments illustrated in Figures 3 to 5 di~fer
- from those illustrated in Figures 1 and 2 in several ways an~
: some of the modifications shown in Figure 3 may equally well
be applied to the Figure 1 and 2. For example, the partition
32 of the embodiment of Figures 1 and 2 is formed by an annu-
lar flange projecting inwardly from the periphery 18 of the
chamber or housing 12 whereas in Figure 3 this flange 32 has
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been replaced by a circular flange 46 projecting in from the
- front wall 14 of the housing. Alternatively the flanges 32
and 46 may be eliminated and the chipper housing be divided
by the disc per se, i.e. the clearance between the periphery
of ~he disc 20 and, the periphery 18 of the housing 12 would
be sufficiently small for the disc 20 alone to effectively
divide the housing into the front chamber 36 of the rear
chamber 34. A proven way to construct the partition is to
form a labyrinth type seal for example by forming a grove in
the periphery o the disc and extend the annular partition
32 into the grove.
A further modification is shown in Figures 3 to 5
inclusive in that instead of the debris outlet 40 extending
tangentially from the housing 12 through the circumferential
wall 18 the debris outlet 50 has been provided by a hole 52
through the front wall 14. It will be noted from Figure 5
tbat the annular flange or ring 46 is omitted in the area of
the outlet 50 and that a separate baffle 54 is provided to
direct to the debris at an angle outward from the front
chamber 36.
The embodiment of Figures 3 to 5 inclusive operates
in the same way as the embodiment of Figures 1 and 2 in that
.
wood is fed into the front of the chipper via inlet 30, is
chipped by the knives 24 with the chips passing through the
disc ~0 into the rear chamber 34 and the debris being drawn
into the front chamber 36 and being carried out through the
outlet 50 by being deflected via the baffle 54. The chips
leave the rear chamber 34 in the conventional manner through
outlet 38.
The disclosure has dealt primarily with chippers
having tangential chip outlets from the housing however,
t~e invention may equally be applied to disc chippers ~ith
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bottom chip outlets provided these chippers are formed with
rear and front chambers and with separate outle~s from these
chambers for the chips and debris.
As is known, the wood material in the branches and,
twigs has markedly inferior quality for pulping than the
bole section. Also the quantity of bark and leaves or ratio
of bark and leaves to wood in small branches or twigs is
very high compared with the remainder of the tree and fur~
ther the majority of grit and dirt gathered during the tree
harvesting operations adheres to the branches. It is there-
', fore desirable for pulping operations to minimize the
' number of branches or twigs that are cut into chips and to
maximize the amount of such material (branches and twigs)
that leave the chipper via the debris outlet. To this end,
' it has been found that by increasing the anvil clearance
(clearance between the anvil and the knife) significantly
the number of twigs and branches drawn into the front
chamber is significantly increased. For example conven-
tionally an anvil clearance of about 0.015 to about 0.04
inches is used, however to increase the number of twigs
`' and branches in the debris this clearance may desirably be
increased to about 0.1 inches but in some case may be in-
, creased even more up to about 0.3 inches.
; Increasing the anvil clearance as above described
facilitates passage of the branches, after or as they are cut
from the tree, into the front chamber and thus reduces the
' number o~ branches which are cut into chips. Twigs or
' branches once they are severed from the tree but without
being chopped, pass into the front chamber through a passage
defined by the clearance between the cutting face and the
adjacent end of the infeed spout i~e. not all of these un-
chipped branches and twigs need pass through the anvil clear~
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ance which defines only one side of the passage from the in-
feed spout to the front chamber. Some may pass through the
clearance between the bottom edge of the infeed spout and
the cutting face since such clearance may be substantially
greater than the anvil clearance. Whatever way the twigs
and branches enter the front chamber, if they are of a longi-
tudinal dimension greater than any of these clearances they
must be moved or positioned substantially parallel to the
cutting face of the disc. This operation may be obtained by 10 the pulling action of the knives as they penetrate only
partly through the branch as determined by the clearance bet-
ween the kni~e and the anvil. In any event, it is apparent
that they must deviate from the direction in which they are
advanced into the chipper and at least partly align or
orient themselves with the face o~ the chipper disc to per-
mit them to pass from the infeed spout into the front chamber.
The distance between the front cutting face 25 of
the disc and the inner face of the front wall of the housing
should be at least 1 inch to provide an adequate size front
chamber for reasonable operation. Generally this dimension
will not be greater than about 3 inches since incrPasing the
dimension beyond 3 inches does not provide any additional
advantages.
The disclosure has referred to whole tree chipping
which is intended to incluae not only whole trees, but also
discrete tree sections such as tops only but with branches
and twigs integral therewith.
Whole tree chippers with substantially flat or
radial cutting faces have been described, however, the in- ,
vention may also be applied to modi~ied disc type chippers
such as the so called V drum whole tree chippers, but the
radial disc has proved more effective~
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Modifications may be made without departing from
the spirit of the invention as def ined in the appended
claims .
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