Note: Descriptions are shown in the official language in which they were submitted.
1076()~6
FIELD OF THE INVENTION
The present invention relates to a wood chipper,
more specifically the present invention relates to an impro-
ved wood chipper for separating debris from chips during the
chipping operation.
PRIO~ ART
Applicant's previously filed Canadian Patent
1,029,284 issued April 11, 1978 discloses a debris separating
chipper comprising of a rotor having a cutting face that
forms one wall of a front or debris chamber which has a
debris outlet. Chips cut by the knives on the rotor are
conveyed away from the front chamber into a chip space or
chamber and are rejected from the chipper through a separate
chip outlet whereby chips and debris are separated and are
ejected from the chipper in separate streams through their
respective outlets.
Conventional disc type chippers are provided with
impellor blades at the back of the disc which draw air
through the back wall of the housing into the chip chamber
and blow it out with the chips through the chip outlet. The
pumping effect created by these blades also draws air in
through the knife slots (the slots leading each knife and
through which the chips pass after they are cut) and this air
drawn through the knife slots entrains small debris particles
including grit leaves needles lose bark etc. into the chip
chamber where they remix with the chips.
It has also been proposed to provide chip pockets
on the rear face of the disc to receive chips cut by the
chipper knives and prevent them from hitting the rear face of
the chipper housing (see for example Canadian patent 962,921
issued Feb. 18/75 to Gaitten). These pockets hold the chips
until the chip outlet is reached and then ejects them di-
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A
107601)6
rectly into the chip outlet. These chip pockets, by
preventing impact of the cuts chips against the rear facè of
the housing, reduce chip damage during the chipping
operation.
It has also been proposed in an earlier Canadian
patent 759,747 issued May 30, 1967 to Kirsten to provide chip
pockets, to open the pockets to the atmosphere and to provide
a volute housing whereby air is pumped through the pockets as
the disc rotates. It will be apparent that any air entering
the pocket will tend to enter adjacent axes of rotation and
be ejected tangentially from the periphery.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides an improvement
over the separator disc chipper described in Canadian patent
1,029,284 referred to hereinabove by providing air flow
through the chip slot into the front or debris chamber and
thereby substantially eliminating the possibility of en-
trainment of light material through the chip slot and in some
cases to actually blow material away from the slot so that it
cannot pass through the slots into the accepted chip area. It
is also possible to traverse the chip path with a jet of air
to deflect and thereby separate light material passing with
the chips and reject this material with the debris.
Broadly, the present invention relates to a chip-
per comprising a housing, a disc mounted for rotation in said
housing, said disc having a cutting face, at least one knife
on said cutting face, a debris chamber formed between said
cutting face and said housing, a slot through said cutting
face for passage of chips cut by said knife to a chip space
separated from said debris chamber, a debris outlet from said
debris chamber for ejecting debris from said chipper, and a
separate chip outlet communicating with said space for
removal of chips from said chipper, the improvement com-
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- 1076006
comprising means for providing air under pressure, a compart-
ment on said rotor adjacent said slot, means for directing
air from said means for providing air under pressure to said
compartment so as to eject air from said compartment through
said slot towards said debris chamber, whereby air flows
through said slot into said debris chamber during at least a
substantial portion of the revolution of said disc.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features, objects and advantages will be
evident in the following detailed description of the preferred
embodiments of the present invention taken in conjunction with
the accompanying drawings in which;
Figure 1 is a schematic elevation view of a chipper
constructed in accordance with the present invention.
Figure 2 is a section along the line 2-2 of Figure
1.
Figure 3 and 4 are sections along line 3-3 of Figure
1, illustrating two modifications incorporating the present
invention.
Figure 5 is a view similar to figures 3 and 4 illus-
trating a more sophisticated arrangement of *he present inven-
tion and is a partial section along the lines 5-5 of figure
6.
Figure 6 is a section along the lines 6-6 of figure
5.
Figure 7 is a section along the lines 7-7 of figure
6.
Figure 8 is a section along the line 8-8 of figure
7.
Figure 9 is a view similar to figure 5 illustrating
the preferred and simplest arrangement of the present invention.
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Figure 10 is a partial section along the lines
10-10 of figure 2.
Referring to Figures 1 & 2 the chipper is formed
of housing 10 having a peripheral wall 12, a front wall
and a rear wall 16. A chipper disc 18 is rotably mounted
within the housing on a suitable shaft 20 and divides the
housing 10 into a front or debris chamber 22 and a rear cham-
ber 24. An internal annular partition wall 23 combines with
the disc 18 to isolate the front and rear chambers 22 and 24
so that substantially the only communication between the two
is through the knife slots 36 as will be described hereinbe-
low. A tangential outlet 26 is provided adjacent a front
wall 14 in communication with the front chamber 22 and
functions as a debris outlet for debris entering the front
chamber 22. A tangential chip outlet 28 communicates with a
read chamber 24 and provides an outlet for chips cut by the
chipper.
A feed inlet 30 is provided through the front
wall 14 for feeding logs to the chipper disc 18.
The chipper disc 18 has a front cutting face 32
mounting at least one knife 34. In the illustrated arrange-
ments a knife slot 36 extends through the disc 18 to the
back-face 38 thereof and is positioned immediately adjacent
and in front of each knife 34 so that chips cut by the knife
34 may pass through the disc 18 via the passage 36.
In the embodiment of figures 2 to 4 positioned on
the back of the disc to receive the chips passing through the
disc via each slot or passage 36 is a chip compartment or
pocket 38 (see also Figures 3 & 4). These chip pockets 38,
as will be apparent from Figures 3 & 4 may be smaller adja-
cent the shaft 20 and taper so that they expand at a substan-
tially uniform rate toward the peripheral wall. The outer
edge 40 of each pocket 38 conforms with the inner periphery
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of the peripheral wall 12 and is positioned relatively close
to this wall 12 thereby to inhibit the flow of air from the
pockets 38 except through the slots 36, throughout a major
portion of the rotation of the disc 18 and except when the
pocket 38 is in communication with the chip outlet 28.
An angular ring 42 interconnects the narrow ends
of all pockets 38. This angular ring 42 is provided with
apertures 44 substantially radially communicating the inside
of the ring 42 with each pocket 38 i.e. an aperture 44 is
provided at the narrow end of each of the pockets 38.
Within the angular ring 42 may be mounted a valve
disc 46 which is connected to a plenum chamber 48 that sur-
round the shaft 20. The plenum chamber 48 is connected by a
pipe 50 to an air compressor 52 which in the illustrated
arrangement is shown driven by the shaft 20. Communication
between the plenum chamber 48 and each of the pockets 38 is
governed by the valve disc 46 which is cut away as indicated
at 54, so that communication between the plenum 48 in each of
the pockets 38 may be controlled as desired i.e. when the
aperture 44 are aligned with the cut way area or areas 54.
It shouId be noted that in some cases the valve
disc 46 may be eliminated so that the plenum 48 simply com-
municates directly with the inside of the angular ring 42 and
each of the pockets 38 is constantly in communication with
the plenum 48, see particularly the figures 5 to 9 embodi-
ments. In the figures 2 to 4 embodiments it is preferred to
isolate each pocket 38 from the plenum 48 as the radial out-
let of each pocket communicates with the chip outlet 28 by
providing solid areas on the valve disc 46 at the location ;
when each pocket is ejecting through outlet 28 (see fig. 10).
It will be apparent from Figures 3 & 4 that the
pocket 38 may be positioned in front of the slot 36 in the
direction of movement of the disc as shown in figure 3 or
` 1076~06
alternatively toward the rear of each slot 36 as indicated at
38a in Figure 4.
As indicated in Figure 2, suitable apertures 56
may be provided in the rear wall 16 to permit air to be drawn
in through the rear wall into the rear chamber 24 in the
spaces between the pockets 38 (which will function as vanes)
and facilitate the pumping of air out through chip outlet 28
-- thereby to aid in conveying the chips. Also it will be noted
that blades or paddles 58 are provided on the disc 18 in the
front chamber 22 to aid in ejecting debris through the outlet
26.
In the embodiments shown in figures 5 to 9 inclu-
sive, the pockets 38 are optional as indicated by the dotted
line in figure 5 and these pockets need not be connected with
the source of air under pressure.
Referring specifically to the embodiment illus-
trated in figures 5 to 8 inclusive which is the more elabor-
ate embodiment of the present invention incorporating a
further separation stage for dust and fines separation
subsequent to cutting of the chips. It will be noted that
the pockets 38 have been replaced by paddles 100 which in the
illustrated arrangement project from a structure 102 that
forms a dust chamber 104 on the back side of the disc 18.
Paddles 100 need not be integral with the housing 102 and
could in fact be spaced therefrom rearwardly in the direction
of rotation of the disc 18. As shown in figure 6 and 7 the
structure 102 (in the illustrated arrangement only one such
structure is shown, however in a multi-knife chipper there
would be one such structure for each knife) are
interconnected at their outer periphery by an annular flange
106 which projects rearwardly from disc 18. The flange 106
co-operates with the partition 23 to seal the front chamber
22 from the rear chamber 24 as illustrated in figure 7.
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Each of the dust chambers 104 communicates with
the front chamber 22 via the peripheral outlet 108 which is
formed through the rim 106 between the partition wall 23 and
the rear face of disc 18.
A nozzle 110 is formed by an elongated slot in a
duct 112 having an internal compartment 114 which communi-
cates with the front end of chamber 48, which as above de-
scribed is supplied with air from the blower 52 via pipe 50
(see figure 2), through the opening 116 (see figure 6) in the
arrangement of figures S to 9 inclusive. The front end of
chamber 48 is opened ended and telescopes in sealing relation
with an annular member 118 that is provided with suitable
openings 116 for each duct 112 (one for each knife) on the
chipper disc (only one is shown). This annular member is
similar to the annular ring 42 of the figures 2 to 4 embodi-
ment, however, no valve 46 is necessary in the figures 5 to 9
embodiments since the nozzle 110 functions as a metering
mechanism and can be connected to the source of air pressure
at all times regardless of position of the duct 112 to the
outlet 28 without significantly reducing the pressure in the
duct 112 as the chips are ejected through outlet 28.
The nozzle 110 extends substantially the full
length of the knife slot 36 and is aimed at the edge 129
formed between the trailing wall 120 of the chip slot 36 and
the rear wall 122 (wall opposite the cutting face 35) of the
disc 18. Air flow through the nozzle 110 forms a curtain
across and along the length of the slot 36. The air curtain
in part is deflected out through the slot 36 and in part is
deflected towards the dust chamber 104 when no chips are pas-
sing through the chip slot 36.
In the embodiment of figure 9 in the nozzle 110has been replaced by a similar nozzle 126, however, since the
dust chamber 104 has been eliminated, this nozzle 126 (in the
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form of an elongated slot extending the length of the chip
slot 36) is aimed to direct air as a curtain from the duct
112a into the slot 36 from the leading side of the slot to
deflect off trailing wall 120 and into the front chamber 22.
Also the duct 112a and this compartment 114a have been en-
larged in a direction parallel to the axis of the disc to in-
crease the volume and size of the opening 116 to ensure a
supply of sufficient volumes of air. The duct 112 could be
similarly enlarged in the figures 5 to 9 embodiment.
It will be apparent that the nozzles 110 and 126
are essentially the same and that they form a curtain of the
air extending across the chip slot 36. Flow could be paral-
lel to the slot 36 i.e. not traverse it but the air nozzles
would be more difficult to build and more susceptible to dam-
age and plugging by chips.
In opeeation, wood is fed to the chipper in the
conventional manner via the feed spout 30 and is chipped by
the knives 34. The impacts of these knives against the log
shake debris and like from it, particularly in whole trees
chipping where a significant quantity of bark, grit, small
branches and needles, leaves, etc. are present and may be
separated from the tree and fall into the front chamber 22.
The cut chips pass through the slots 36 into the pockets 38
or rear chamber 23 in the case of figures 5 to 9.
Air is drawn into the blower 52 as indicated by
the arrows 60 and is fed from the blower 52 via line 50 into
the chamber 48.
In the figur~s 2, 3 and 4 embodiment the chamber
48 communicates via the cut away section 54 and apertures 44
or directly through the apertures 44 with the pockets 38 to
force air out through the slots 36 into the chamber 22. The
amount of air that can escape through the outer ends tradial
extremities) of the pockets 38 is limited due to the close
` 10760C~6
fit between the edge 40 and the inner periphery of peripheral
wall 12 of the housing 10, except when the pockets 38 are in
communication with the outlet 28 and the chips and air are
ejected through the outlet 28. Also in some cases ~when
apertures 56 are provided), air may be sucked in through the
openings 56 in the back wall 18 into the spaces between the
pockets 38 and blown out through the outlet 28 with the
chips. Not too much air will be drawn in this way since the
spaces between the pockets 38 are sealed in substantially the
same manner as the pockets 38 except in the area of the out-
let 28. In the event a greater air flow from between the
pockets 38 is desired, rear wall 16 should be moved to in-
crease the size of chamber 24 and provide more clearance be-
tween the pockets 38 and the rear wall and thereby permit air
from between the pockets to expand and be forced out the out-
let 28 during substantially the full rotation of the disc
also paddles could be added in the spaces.
Debris in the front chamber 22 is ejected from
the housing 10 through the outlet 26 by means of the paddles
- 58. The air pressure within the pockets 38 injects air
through the slots 36 into the chamber 22 which substantially
eliminates the tendency for small dust particles and like de-
bris to be entrained into the pockets 38 and remixed with
chips (as would be the case in a conventional chipper not in-
corporated to the present invention) and thereby ensuring
better separation of the debris from the chips.
The operation of the figures 5 to 9 embodiments
is basically the same as the operation of the embodiments of
figures 2 to 4 inclusive. ~owever, in the figure 5 to 7 ar-
rangement, the air from the nozzle 110 when no chips arebeing cut deflects in part into the chip slot 36 and into the
dust chamber 104. When chips are being cut they block the
passage 36 i.e. when the knife 34 is cutting, much of the
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1076006
slot is blocked by wood and the air blown through the
passage 36 into the front chamber 22 is reduced whi-ch tends
to deflect the air jet issuing from the nozzle 110 towards
the pocket 104. In any event, even if there is no deflection
of the jet that portion of the jet split by the edge 124 and
which tends to sweep through the stream of chips or around it
into the chamber 104 carries with it some of the fines and
dust particles accompanying the chips thexe~-further cleaning
the chips. The chips themselves are not deflected significantly
as their inertia is too high and they travel substantially in
their normal trajectory into the back chamber 24 from which
they are ejected by the paddles 100.
The fines and light materials entering the dust
chamber 104 move radially outward along this chamber 104 and
pass through the outlet 108 at the circumference of the disc
into the front chamber 22 and are ejected through the debris
opening 26 by the paddles 58.
In the embodiment of figure 9, there is no further
separation of fines and dust of the chips. Directing the air
jet or curtain issuing from the nozzle 126 into the slot 136
also similar to the air ejected through the slots 36 in the
5 to 7 embodiment and effectively prevents the sucking of air
in through the slot by the pumping action of the vanes lQQ _
and any tendency for material to be entrained through the
slots and contaminate the chips is essentially eliminated.
The air flow through the slots 35 should be at the
speed of at least about 1000 ft/min to clear light materials
in the debris chamber from in front of the knife and preferably
above about 5000 ft/min.
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1076~06
In the embodiments of figures 5 to 9 the width of the nozzle
should be at least about l/4 inch and preferably above 1/2
inch and the pressure within the duct 112 be at least about 5
inches of water and preferably above 10 inches for low pres-
sure operation. If higher pressures are used smaller nozzles
may be used but this requires more sophisticated blowers.
Only substantially radial introduction of air in-
to the compartments 38, 38a, 114 or 114a have been shown in
the drawings i.e. via an axial passage 48, however, other
modes of air introduction may be used. For example in the
fig 1 to 4 embodiments a plenum chamber could be provided be-
hind the rear wall 16 of the housing and the rear wall be
provided with a slot equivalent to the slot 54 adapted to
communicate with the pockets 38 through suitable holes in the
rear wall of the pockets 38 positioned in alignement with the
slot. This construction would require some form of slot
- sealing means mounted on the disc 18 (such as a radial wall)
between the holes leading into circumferentially adjacent
pockets.
The term "disc" in relation to the chipper rotor
as used herein is intended to include discs with a planer
(radial) cutting face as well as those with conical cutting
faces including rotors formed by a pair of conical discs
combined to form what is sometimes referred to in the trade
as a V-drum chipper
Modifications will be evident to those skilled in
the art without departing from the spirit of the invention as
defined on the appended claims.
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