Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CA 02299479 2000-02-24
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MACHINE FOR CONVEYING LUMBER OR LOGS OF WOOD
FIELD OF THE fNVENTION
The present invention relates to a machine for conveying lumber or logs of
wood in wood transformation industries such as sawmills.
BACKGROUND
In sawmills, lumber and logs of wood need to be conveyed between various
stations, some of which are at, different levels, implying that the lumber and
logs must be lifted from one level to another.
Different types of apparatuses for conveying the logs of wood, whether or not
the bark is still present on the log, exist. These apparatuses are also used
for
dropping the logs of wood one by one on a strap conveyor directed
perpendicularly to the conveying direction of the apparatus, in such a way
that
the logs of wood are positioned end-to-end thereon for feeding a wood
transformation machine.
One known type of apparatus for conveying logs of wood comprises an
inclined panel, on which are operatively mounted several driving belts, which
are positioned laterally. The driving belts have protruding lugs all along
their
length that are designed and positioned in such a way that a log of wood may
be carried on a set of aligned lugs and conveyed upwardly by the motion of the
driving belts.
One type of apparatus for conveying lumber is known and used in sawmills,
and functions similarly to one of the known types of apparatus for conveying
logs of wood previously described. This type of apparatus for conveying lumber
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may carry one or more pieces of lumber at the same time. At the exit, the
lumber is transferred on a strap conveyor directed in parallel to the
conveying
direction of the apparatus and the pieces of lumber are accumulated side-by-
side on the strap conveyor.
Another known type of apparatus for conveying logs of wood is called the
"step-feeder". US patents 5,374,157, 3,168,190 and 5,678,681 disclose
different apparatuses of the "step-feeder" type.
The apparatuses described in US patents 3,168,190 and 5,678,681 have one
large staircase with several stairs moving independently, in such a way that
two adjacent stairs move up and down oppositely alternately. It results that
when a log is carried by one stair moving upwardly, it is transferred to the
following stair which just moved downwardly in order to pick up the log and
move upwardly to transfer the log to the next upstream stair, and so on.
The apparatus described in US patent 5,374,157 uses the same principle as
the one described in US patents 3,168,190 and 5,678,681, but it uses several
staircase-like-structures placed side-by-side. Alternately, each staircase-
like-
structure moves independently up and down by a predetermined distance. They
are divided into two sets: a first set, and a second set being intercalate
between the staircase-like-structures of the first set. When the first set of
staircase-like-structures moves down, the second set of staircase-like-
structures moves up. These movements define an arc of a circle respectively.
In operation, a log of wood is carried upwardly by the aligned stairs of one
set
of staircase-like-structures, while the second set of staircase-like-
structures
moves down until an aligned stair of this second set picks up the log of wood
and carries it upwardly until an upstream aligned stair of the first set of
staircase-like-structures picks up the log of wood and moves it upwardly, and
so on.
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The above-described apparatuses for conveying lumber or logs of wood have
many drawbacks. One drawback of these apparatuses is their complex
mechanics, which break frequently. The constitutive pieces are subject to
wear, and the apparatuses require constant maintenance.
Another drawback is the fact that these apparatuses for conveying lumber or
logs are generally noisy. Having less noise means a better working environment
and possibly less injuries to the workers due to disturbance.
In the case of the known apparatuses for conveying logs of wood, a further
drawback consists in the fact that there exists the possibility of having two
logs of wood carried by the apparatus at the same time, which results in
transferring two logs side-by-side on the strap conveyor. This is inconvenient
since it is necessary to have the logs aligned end-to-end to avoid obstruction
of the transformation machine fed by the strap conveyor. The possibility of
two
logs being carried at the same time is frequently caused by a curved log or a
log that still has bark, which rolls to a downstream step and is conveyed
together with the downstream log.
Still in the case of the known apparatuses for conveying logs of wood, an
additional drawback is their inability to convey the logs of wood at a high
speed. Some of the apparatus known in the field cannot convey the logs at a
speed higher 55 logs per minute. The fact that a curved log or a log with bark
rolls down one step or more in some of the known apparatus, represents an
additional factor which slows down the conveying speed.
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SUMMARY OF THE INVENTION
The present invention is directed to a machine that overcomes one or more of
the above-mentioned drawbacks.
In accordance with the present invention, there is provided a machine for
conveying elongated wooden pieces. Each wooden piece has a width falling
within a given range. The machine comprises:
- a frame having two opposite sides, a front and a back, the wooden
pieces being conveyed in a conveying direction from the front towards the back
of the frame;
- at least two parallel conveying shafts rotatably mounted on the frame,
and being substantially perpendicular to the conveying direction, each shaft
having an axis of rotation;
- rotating means far rotating each shaft about said axis of rotation at a
desired speed in a direction corresponding to the conveying direction; and
- at least two toothed circular plates mounted on each shaft, each plate
having a radius and extending in a plane crossing the axis of rotation of the
shafts, the plates of a shaft being offset with respect to the plates of an
adjacent shaft, each tooth of each plate being spaced apart from an adjacent
tooth by a distance which corresponds substantially to the range of diameter
of the wooden pieces and defining a space therebetween for receiving at least
a portion of a wooden piece, the teeth of the plates mounted on a same shaft
being aligned;
- wherein each shaft is spaced from an adjacent shaft by a distance at
least equal to the radius of a toothed plate.
In accordance with the present invention, there is also provided a machine for
conveying logs of wood. Each log of wood has a width falling within a given
range. The machine comprises:
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- a frame having two opposite sides, a front and a back, the logs being
conveyed in a conveying direction from the front towards the back of the
frame;
- at least two parallel conveying shafts rotatably mounted on the frame,
5 and being substantially perpendicular to the conveying direction, each shaft
having an axis of rotation;
- rotating means for rotating each shaft about said axis of rotation at a
desired speed in a direction corresponding to the conveying direction; and
- at least two toothed circular plates mounted on each shaft, each plate
having a radius and extending in a plane crossing the axis of rotation of the
shafts, the plates of a shaft being offset with respect to the plates of an
adjacent shaft, each tooth of each plate being spaced apart from an adjacent
tooth by a distance which corresponds substantially to the range of diameter
of the logs and defining a space therebetween for receiving at least a portion
of a log, the teeth of the plates mounted on a same shaft being aligned;
- wherein each shaft is spaced from an adjacent shaft by a distance at
least equal to the radius of a toothed plate.
In accordance with the present invention, there is further provided a machine
for conveying lumber. Each lumber has a width falling within a given range.
The
machine comprises:
- a frame having two opposite sides, a front and a back, the lumber
being conveyed in a conveying direction from the front towards the back of the
frame;
- at feast two parallel conveying shafts rotatably mounted on the frame,
and being substantially perpendicular to the conveying direction, each shaft
having an axis of rotation;
- rotating means for rotating each shaft about said axis of rotation at a
desired speed in a direction corresponding to the conveying direction; and
- at least two toothed circular plates mounted on each shaft, each plate
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having a radius and extending in a plane crossing the axis of rotation of the
shafts, the plates of a shaft being offset with respect to the plates of an
adjacent shaft, each tooth of each plate being spaced apart from an adjacent
tooth by a distance which corresponds substantially to the range of diameter
of the lumber and defining a space therebetween for receiving at least a
portion
of a lumber, the teeth of the plates mounted on a same shaft being aligned;
- wherein each shaft is spaced from an adjacent shaft by a distance at
least equal to the radius of a toothed plate.
In accordance with the present invention, there is also further provided a
machine for separating and conveying logs of wood where each log has a
diameter falling within a given range and the machine comprises:
- a frame having two opposite sides, a front and a back, the logs of
wood being conveyed in a conveying direction from the front towards the back
of the frame;
- at least three parallel conveying shafts rotatably mounted on the frame,
and being substantially perpendicular to the conveying direction, each
conveying shaft having an axis of rotation, all the shafts extending in an
inclined plane so that the back of the frame is higher than the front of the
frame and the conveying direction is oriented upwardly ;
- rotating means for rotating each shaft about its axis of rotation at a
desired speed in a direction corresponding to the conveying direction;
- at least two notched circular plates mounted on a most upstream shaft,
each notched plate having a circumference being provided with a plurality of
thin notches;
- at least two toothed circular plates mounted on each shaft being
downstream from the most upstream shaft, each tooth being spaced apart
from an adjacent tooth by a distance which corresponds substantially to the
range of diameter of the logs of wood, and defining a space therebetween for
receiving at least a portion of a log, the teeth of the plates mounted on a
same
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shaft being aligned;
- a shelf on the front of the frame for receiving a bundle of logs of wood;
and
- two side walls mounted on each opposite side of the frame and
extending upwardly, the walls defining with the shelf a separating and
conveying area;
- wherein each of the toothed plates and the notched plates has a radius
and extends in a plane crossing to the axis of rotation of the shaft on which
it
is mounted, the plates of a shaft being offset with respect to the plates of
an
adjacent shaft; and
- wherein each shaft is spaced from an adjacent shaft by a distance at
least equal to the radius of a toothed plate or the radius of a notched
plates.
The invention and its advantages will be better understood upon reading the
non restrictive description of the preferred embodiments of the present
invention. This description is given with reference to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a first preferred embodiment of the
invention.
Figure 2 is a perspective view of a second preferred embodiment of the
invention.
Figure 3 is a cross-sectional view of the first preferred embodiment of the
invention.
Figure 4 is a side view of the first preferred embodiment of the invention.
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Figure 5 is a side view of a third preferred embodiment of the invention.
Figure 6 is a cross-sectional view of a fourth preferred embodiment of the
invention.
Figure 7 is a cross-sectional view of a fifth preferred embodiment of the
invention.
Figures 8 A, B, C, D, E, F and G are views of seven different conveying
plates.
Figure 9 is a cross-sectional view of a sixth preferred embodiment of the
invention.
Figures 10 A, 10 B and 10 C are temporal sequences of a portion of the view
shown in Figure 9 showing the interaction of the obstructing member with two
logs being carried at the same time.
Figure 1 1 is a cross-sectional view of a seventh preferred embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention, as mentioned above, concerns a machine ( 10) for
conveying elongated wooden pieces (1 ) from one level to another. It is to be
understood that a wooden piece (1 ) includes a log of wood (as illustrated in
Figures 1, 5, 9, 1 Oa, 1 Ob and 1 Oc) or a lumber (as illustrated in Figure 1
1 ). The
log of wood can be with or without bark. The lumber to be conveyed by the
machine (10) of the present invention preferably have a transversal cross-
section of 2 x 4 inches, 2 x 3 inches, 2 x 6 inches, 2 x 8 inches, 1 x 3
inches,
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1 x 4 inches. However, as will be explained hereinafter, the machine ( 10) can
be adapted for other sizes. The lumber can be of various lengths but usually
the
lumber is 8 or 16 feet long.
Referring to Figure 2, the machine (10) comprises a frame (12) having two
opposite sides ( 14), a front ( 16) and a back ( 18). The wooden pieces ( 1 )
are
coriveyed in a conveying direction C from the front (16) towards the back (18)
of the frame (12). The conveying direction C is illustrated in Figures 1, 2,
3, 6
and 7 by a wide arrow C.
Referring to Figure 1, the machine ( 10) comprises at least two parallel
conveying shafts (20) rotatably mounted on the frame ( 12), and being
substantially perpendicular to the conveying direction C. Each shaft (20) has
its own axis of rotation (22). As will be hereinafter described, a chain and
pinion system is used to drive the shafts (20) in rotation, but any other
means
to do so, such as a cam, is contemplated by the present invention and is well
within the skill of one versed in the art.
in the preferred embodiments of the invention shown in Figures 1 to 7, the
conveying shafts (20) are substantially horizontal. However, it is to be
understood that they can be inclined at an angle with respect to the
horizontal,
i.e. one extremity of the shafts (20) being mounted at a higher level on one
side ( 14) of the frame ( 12) than the other side ( 14). If the angle is too
large,
the logs (1) could slide off the machine (10). In such a case, the side walls
(40), which will be detailed hereinbelow, can prevent the wooden pieces (1 )
from sliding off, if necessary.
Still referring to Figure 1, the machine ( 10) further comprises rotating
means for
rotating each shaft (20) about its axis of rotation (22) at a desired speed in
a
direction R corresponding to the conveying direction C. The direction of
rotation R
of the shaft (20) is illustrated by thin arrows R in Figure 1. Rotating means
can be
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different mechanisms such as hydraulic, air or mechanical mechanisms.
The machine (10) also comprises at least two toothed circular plates (24)
mounted
on each shaft (20). Each plate has a radius U (shown in figure 8A) and extends
in
5 a plane P crossing the axis of rotation (22) of the shafts (20) as shown in
Figure 1.
Different types of toothed plates are illustrated respectively in Figure 8 A,
B, C, D,
E, F and G and other shapes of plates (24) may be used according to the
10 invention. Each tooth (26) of a toothed plate (24) has a shape that can be
symmetrical or asymmetrical, and of different sizes. The plates (24) shown in
Figures 8 A, B, C, D and D are specifically adapted to convey logs of wood and
the ones shown in Figures 8 F and G are more specifically adapted to convey
lumber. The tooth (26) of the plate (24) shown in Figure 8 F has preferably a
height of 1 inch and a width of 5 inches. However, it is to be understood that
the size of the teeth (26) can be chosen in order to optimize the conveying
efficiency of the machine ( 10) with respect to the type of lumber to be
conveyed (i.e. cross-sectional dimension).
As can be seen in Figure 2, the plates (24) of a shaft (20) are offset with
respect to the plates (24') of an adjacent shaft (20'). As illustrated in
Figures
1 and 8A, each tooth (26) of each plate (24) is spaced apart from an adjacent
tooth (26') by a distance which corresponds substantially to the range of
diameter of the wooden pieces (1 ) and defining a space therebetween for
receiving at least a portion of a wooden piece (1). It is to be understood
that
the wooden piece ( 1 ) can be completely or partially recessed between two
adjacent teeth (26) of a plate (24) in order to be carried by the plate (24).
The
teeth (26) of the plates (24) mounted on a same shaft (20) are aligned
together
as shown in Figure 1, so that a wooden piece ( 1 ) can be simultaneously
recessed between two adjacent teeth (26) of the plates (24) of the same shaft
(20).
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As illustrated in the side views of Figures 3 to 7 and referring more
particularly
to the numbering on Figure 4, each shaft (20) is spaced from an adjacent shaft
(20') by a distance at least equal to the radius U (shown in Figure 8A) of a
toothed plate (24).
The rotation of the conveying shafts (20) is synchronised in such a way that
a wooden piece (1 ) inserted between a guiding tooth (26) and a following
tooth
(26') of the conveying plates (24) of one shaft (20) is conveyed in the
direction
of rotation R of this shaft {20) until a following tooth (26') of the plates
(24) of
an adjacent downstream shaft (20) carries the wooden piece (1 ). Thus, the
wooden pieces (1 ) is transferred to the adjacent shaft (20) and is now
engaged
and carried between the following tooth (26') and a guiding tooth (26) of the
plates (24) of the adjacent downstream shaft (20). Therefore, the adjacent
downstream shaft (20) conveys the wooden piece (1 ) further with respect to
the conveying direction C.
Referring more particularly to Figures 3 and 6, the machine ( 10) further
comprises an additional shaft (30) which is rotatably mounted on the frame
2 0 ( 12) and located upstream position of the at least two conveying shafts
(20)
of the machine ( 10) according to the invention. The two preferred
embodiments of the machine (10) illustrated in Figures 3 and 6, comprise five
conveying shafts (20) but, for the sake of clarity, only two are identified by
a
reference number. "Upstream" position refers to the conveying direction C;
thus "upstream" is closer to the front (16) and "downstream" is closer to the
back (18) of the machine (10).
Referring now to Figure 1, the additional shaft (30) has an axis of rotation
(32)
which is parallel to the axis of rotation (22) of the conveying shafts (20).
The
machine (10) also comprises rotating means for rotating the additional shaft
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(30) about its axis of rotation (32) in a direction R' corresponding to the
conveying direction C. Rotating means can be embodied in different
mechanisms, as mentioned above with respect to the rotating means of the
conveying shafts (20).
Referring to Figures 1 and 2, at least two notched circular plates (34) are
mounted on the additional shaft (30) and in the preferred embodiments of the
machine ( 10) illustrated in these figures, five notched plates (34) are
mounted
on the additional shaft (30). As indicated in Figure 3, each notched plate
(34)
has a radius U' and a circumference being provided with a plurality of thin
notches (36). As indicated in Figure 1, each notched plate (34) extends in a
plane P' crossing the axis of rotation (32) of the additional shaft (30). The
notched plates (34) are offset with respect to the toothed plates (24) of a
most
upstream conveying shaft (20"). The additional shaft (30) is spaced from the
most upstream conveying shaft (20") by a distance at least equal to the
longest one of the radius U of a toothed plate (24) and the radius U' of a
notched plate (34).
According to a preferred embodiment of the invention, each notched plate (34)
of the additional shaft (30) has about 50 notches (36) and a radius U' longer
than the radius U of each toothed plate (24) of the conveying shafts (20).
The presence of the additional shaft (30) and the notched plates (34) mounted
thereon is a preferential feature of the machine (10) and is more particularly
2 5 useful for a machine ( 10) being designed to convey logs of wood ( 1 ).
This
preferential feature is shown in the first, second, third, fourth and sixth
preferred embodiments of the invention shown in Figures 1 to 6 and 9. The
presence of the additional shaft (30) and the notched plates (34) makes the
logs ( 1 ) rotate about themselves and helps to separate the logs ( 1 ) and
engage
them one by one between two adjacent teeth (26 and 26') of the toothed
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plates (24) of the upstream shaft (20). The additional shaft (30) is driven in
rotation at a speed that can differ from the rotation speed of the conveying
shafts (20). Increasing or reducing the speed of rotation of the additional
shaft
(30) helps to manage the accumulation of logs of wood ( 1 ) at the entry of
the
machine (10). Figure 7 shows an alternative embodiment of the invention
(namely the fifth preferred embodiment of the invention illustrated in the
drawings) where the additional shaft (30) and the notched plates (34) are not
included in the machine ( 10).
According to a preferred embodiment of the invention, each plane P in which
each toothed plate (24) of the conveying shafts (20) extends, defines an angle
with respect to the axis of rotation (22) of each conveying shaft (20) which
is
comprised between 75 and 90 degrees. In the preferred embodiments
illustrated in Figures 1 and 2, the angle defined by the plane P and the axis
(22)
is 90 degrees.
As shown in Figures 1 to 7 and 9, the machine (10) preferably comprises a
shelf (38) on the front (16) of the frame (12) for receiving and holding the
wooden pieces (1). The shelf (38) is useful for holding a bunch of wooden
pieces (1 ) in such a way that one or more wooden pieces (1 ) are in contact
with the plates (24 or 34) of a most upstream shaft (20 or 30).
Referring to Figures 1 to 7 and 9, the machine ( 10) preferably comprises side
walls (40) mounted on each opposite side (14) (indicated in Figure 2) of the
frame (12) and extending upwardly. The side walls (40) with the shelf (~38)
define a conveying area.
Preferably, all the conveying shafts (20), and the additional shaft (30) if
this is
the case, lie in a plane (28). This plane (28) can be horizontal or inclined
so
that the conveying direction C can be horizontally, upwardly or downwardly
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oriented. When the conveying direction C is horizontally or upwardly oriented,
the plane defines an angle with the horizontal which is preferably comprised
between 0 and 50 degrees, so that the back (18) of the frame is at a level
equal to or higher than the front (16) of the frame (12). More preferably, the
shafts (20 and 30) lie in a plane (28) defining an angle of 40 degrees with
the
horizontal. in the first preferred embodiment shown in Figures 3 and 4, the
shafts (20 and 30) are aligned in an inclined plane (28) so that the conveying
direction C is upwardly oriented, and in the fourth preferred embodiment shown
in Figure 6, the shafts (20 and 30) are aligned in a horizontal plane (28).
However, it is to be understood that other layouts of the shafts (20 and 30)
are possible according to the invention, and one example is given in Figure 7
where the three first upstream shafts (20) lie in an inclined plane and the
other
downstream shafts (20) lie in horizontal plane.
According to a third preferred embodiment of the invention shown in Figure 5,
the conveying shafts are separated into two distinct groups where one is
upstream and the other is downstream. This third preferred embodiment is
specific to a machine (10) that conveys logs of wood (1 ). The upstream group
comprises at least two upstream conveying shafts (20u) lying in a first plane
(28'). The downstream group comprises at least two downstream conveying
shafts (20d) lying in a second plane (28"). Preferably, both planes (28' and
28") are inclined with respect to the horizontal and parallel to each other,
and
the second plane (28") is spaced from the first plane (28') so that the logs
of
wood (1) are conveyed upwardly by the upstream conveying shafts (20u), and
then are dropped onto the downstream conveying shafts (20d) which convey
these dropped logs (1 ) upwardly. Advantageously, the additional shaft (30) is
aligned with the plane (28') of the upstream conveying shaft (20u).
Still referring to Figure 5, the machine (10) preferably comprises a log
receiving
area (42) between the upstream conveying shafts (20u) and the downstream
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conveying shafts (20d) for receiving and holding the logs (1 ) conveyed by the
upstream conveying shafts (20u) prior to the logs ( 1 ) being conveyed by the
downstream shafts (20d). Depending on the relative position of the
downstream shafts (20d), the upstream shafts (20u) and their relative speed
5 of rotation, the log receiving area (42) may be optional. Advantageously,
the
log receiving area (42) is a plate as illustrated in Figure 5.
Preferably, the downstream conveying shafts (20d) are driven in rotation at a
speed higher than the speed of rotation of the upstream conveying shafts
10 (20u). This is a preferred feature since it avoids (or prevents) conveying
two
logs (1 ) at the same time. In such a case, the logs (1 ) conveyed two by two
by the upstream conveying shafts (20u) are dropped on the log receiving area
(42). Then, the downstream conveying shafts (20d) which rotates at a higher
speed, picks up the log (1 ) on the area (42) one by one so that the logs (1 )
will
15 not accumulate on the area (42). Moreover, this preferred feature allows
the
machine ( 10) to convey the logs ( 1 ) at a higher rate.
In practice, the upstream conveying shafts (20u) are preferably driven in
rotation at a speed of 55.25 RPM and the downstream conveying shafts (20d)
are preferably driven in rotation at a speed of 56.00 RPM. The differential
speed given to the shafts (20u and 20d) can be caused by different
mechanisms such as the variation of the diameter of the pinion (48) engaging
the driving chain (50) (shown in Figures 2 and 5), or having a separate chain
and pinion system for each group of conveying shafts (20u and 20d), or any
2 5 ~ other appropriate means.
Referring to Figure 2, the machine ( 10) according to a preferred embodiment
of the invention, also comprises a tray (44) that overlies the conveying
shafts
(20), and the additional shaft (30) if there is one. The tray (44) has slots
(46)
therein for receiving the toothed plates (24), and the notched plates (34) as
the
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16
case may be, so that these plates (24 and 34) project upwardly through the
slots (46). The tray (44) is advantageously used to prevent a maximum of
wood residues from falling onto the mechanism of the machine (10).
According to a sixth preferred embodiment of the invention shown in Figure 9,
the machine (10) further comprises a plurality of obstructing members (52),
mounted on the tray (44) and protruding between the plates (24) of two
adjacent conveying shafts (20) in order to block an additional log of wood
(1')
transferred together with a first log of wood (1 ) from the plates (24') of a
conveying shaft (20') to the plates (24) of an adjacent downstream conveying
shaft (20) from being conveyed with the first log of wood (1 ). The use of the
obstructing members (52) on the machine ( 10) is specific to a machine ( 10)
designed to convey logs of wood (10) and is a way to reduce the possibility of
carrying two logs (1 and 1') at the same time, as will be detailed herein
below.
Figures 10a, 10b and 10c illustrate the effect of the obstructing members
(52).
The obstructing members (52) have a given shape and a given location (such
as shown in the Figures) between the plates (24 and 24') of two shafts (20
and 20') so that they take a certain room in the space defined by the tooth
(26) of the plates (24) and the tooth (26') of the following plates (24')
during
the log transfer time, as shown in Figure 1 Oa. When two logs ( 1 and 1 ') are
conveyed together, one log (1 ) goes over the obstructing members (52) and the
second one (1') stays back and leans on the obstructing members (52) as
shown in Figure 10a. The obstructing members (52) keep the second log (1')
back so that the tooth (26') of the upstream plates (24') will not engage the
second log (1'), as shown in Figures 10b and 10c.
Referring again to Figure 9, the shape of the conveying plates (24) of the
machine (10) can vary from one shaft (20) to the other. One way to prevent
that two logs (1 and 1') are carried at the same time, is to preferably mount
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17
conveying plates (24) of the shape shown in Figure 8 E on the most upstream
conveying shaft (20'). Advantageously, the conveying plate (24) shown in
Figure 8 E has round teeth (26) that can pick up a log of wood ( 1 ) and let a
second log of wood (1') roll down the plate (24). Thus, using conveying plates
(24) as shown in Figure 8 E on the most upstream shaft (20') can help to carry
only one log (1 ) at the time. In the preferred embodiment shown in Figure 9,
the other conveying shaft (20) does not have plates (24) of the type of
Figure 8 E.
Although preferred embodiments of the invention have been described in detail
herein and illustrated in the accompanying drawings, it is to be understood
that
the invention is not lirnited to these preferred embodiments and that various
changes and modifications could be made without departing from the scope or
spirit of the invention as defined in the appended claims.
