Note: Descriptions are shown in the official language in which they were submitted.
CA 02648608 2009-01-09
APPARATUS AND METHOD FOR CONVEYING A SHEET
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for conveying a
sheet.
More specifically, the invention relates to a method for successively
conveying a series of
sheets, such as veneer sheets, wherein a sheet being conveyed by a first
conveyer is transferred
to a second conveyer without subjecting the sheet to a tension acting in the
sheet conveying
direction and also to an apparatus for practicing the method.
In stacking sheets into a pile, it takes a given length of time for one sheet
to be stacked
completely onto the top of the pile of sheets. In conveying a series of sheets
successively and
subsequently stacking them one after another uninterruptedly into a pile, any
two adjacent
sheet being conveyed must be spaced apart for a distance that is long enough
to prevent a sheet
from arriving at the stacker while its preceding sheet is still in the process
of being stacked and
from hindering the stacking motion of the preceding sheet. To prevent such
trouble, it has been
practiced to enlarge the spacing between any two adjacent sheets being
conveyed so that the
time interval before a sheet arrives at the stacker after its preceding has
reached the stacker is
longer than the above given length of time that is necessary for a sheet to be
stacked completely.
Alternatively, a series of sheets being conveyed are divided into two
different conveyance
paths each having a stacker and every other sheet is transferred to each of
the path. In stacking
sheets at each of the stackers, a long time is allowed for a sheet comes to
the stacker after its
preceding sheet has been stacked.
Referring to FIG 28 showing a known veneer sheet stacking apparatus according
to
the background art pertaining to the present invention, numeral 100 designates
a first conveyer
moving at a speed vl0 and numeral 101 a second conveyer disposed in alignment
with the first
conveyer 100 and moving at a speed vl l that is faster than v10. A plurality
of veneer sheets
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102 are conveyed by the first conveyer 100 with a relatively small spacing
between any two
adjacent veneer sheets 102. The spacing between the veneer sheets 102 is
enlarged by
transferring them from the first conveyer 100 to the second conveyer 101
traveling faster than
the first conveyer 100.
In such apparatus, however, a veneer sheet 102 just being transferred from the
first
conveyer 100 to the second conveyerl0l is subjected to a tension caused by the
difference in
conveying speeds of the first and second lower conveyers 100 and 101. The
veneer sheet 102
is stretched apart by the tension acting in the direction perpendicular to the
grain of the veneer
sheet and it may be broken and rendered unusable.
The apparatus further includes a third conveyer 103 disposed downstream of and
spaced above the second conveyer 102 at a distance that is greater than the
thickness of the
veneer sheet 102 and overlaps with the second conveyer 101. The third conveyer
103 travels at
a speed v12 that is faster than vl 1. The second conveyer 101 has an air
blower 104 located in
the region overlapping with the third conveyer and operable to blow air
constantly upward.
Reference numeral 105 designates a stop for stopping a veneer sheet being
conveyed by the
third conveyer 103 at a given stacking position and reference numeral 106 a
stacking stand on
which a pile of stacked sheets 102 is supported.
When a veneer sheet 102 being conveyed by the second conveyer 101 enters the
overlapping region of the second and third conveyers 101, 103, it is pressed
against the third
conveyer 103 by air blowing from the blower 104. Then, the veneer sheet 102 is
moved at the
speed v12 in arrow direction by virtue of the frictional force that the veneer
sheet 102 receives
from the third conveyer 103. Air is blown no more against the veneer sheet 102
after it has
moved past the blower 104. Subsequently, the veneer sheet 102 is dropped while
moving
further leftward as seen in the drawing, hits against the stop 105 and then is
dropped onto the
top of the pile of veneer sheets 102.
CA 02648608 2011-07-19
As shown in FIG 28, however, a veneer sheet designated by reference symbol
102a
and subjected to the air blowing from the blower 104 will firstly have its
leading end portion
lifted and pressed against the third conveyer 103. Therefore, the pressed
portion of the veneer
sheet 102a is moved at the speed v12 while the portion of the veneer sheet
102a on the second
conveyer 101 is moved at the speed v11, with the result that the veneer sheet
102a is subjected
to a harmful tension which may cause the veneer sheet, if it is weak against
the tension, to be
broken. Furthermore, the veneer sheet 102a has a middle sloped portion which
is in contact
with neither the second conveyer 101 nor the third conveyer 103 and the weight
of this middle
portion creates tension against the leading end portion of the veneer sheet
102a which is in
contact with the third conveyer 103. As a result, breakage of veneer sheet may
occur.
Therefore, an object of the present invention is to provide an apparatus and a
method
for conveying a sheet which solve the above problems by moving a sheet in its
entire
dimension as measured in the sheet conveying direction in transferring the
sheet from one
conveyer to another conveyer.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above drawbacks and,
therefore,
an object of the present invention is to provide a method and an apparatus for
conveying a sheet
which solve the problems.
In order to achieve the object, the present invention provides an apparatus
for
successively conveying a series of sheets, comprising: a first conveyer for
conveying a sheet
having a leading end and a trailing end in a predetermined direction at a
first speed; a second
conveyer disposed spaced vertically away from the first conveyer at a distance
that is greater
than the thickness of the sheet for conveying the sheet in said predetermined
direction at a
second speed, said second conveyer having a region overlapping with the first
conveyer at least
for a distance corresponding to a dimension of the sheet as measured in said
predetermined
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direction; a plurality of suction members disposed at least in said
overlapping region of the
second conveyer for transferring by suction the sheet in the entirety of said
dimension from the
first conveyer to the second conveyer and holding by suction the sheet against
the second
conveyer, said plurality of suction members being operable simultaneously to
develop suction
substantially over said entirety of the dimension of the sheet; a sheet sensor
for detecting the
arrival of a sheet in said overlapping region and generating a detection
signal indicative of said
arrival; and a control unit operable in response to said detection signal to
activate said plurality
of suction members for the transferring of the sheet and also to deactivate
the suction of each
suction member just after the trailing end of the veneer sheet has moved past
the same.
Transferring the sheet in the entirety of the its dimension along the sheet
conveying
direction, the sheet will not be subjected to a tension tending to stretch the
sheet in the sheet
conveying direction.
In some preferred embodiments of the invention, the second speed of the second
conveyer is faster than the first speed of the first conveyer, so that the
spacing of any two
adjacent sheets being conveyed by the first conveyer is enlarged after they
are transferred
successively from the first conveyer to the second conveyer.
The apparatus of the present invention may include a stacker disposed
downstream of
the overlapping region of the second conveyer as viewed in the sheet conveying
direction for
stacking sheets successively onto a pile of already stacked sheets.
In an embodiment of the present invention, the second speed of the second
conveyer is
set substantially the same as the first speed of the first conveyer and the
first conveyer has an
extension conveyer for conveying every other sheet in a direction other than
the sheet
conveying direction of the first and second conveyers.
The present invention also provides methods of conveying a sheet. The first
method
comprises the steps of a method for conveying a series of sheets, comprising:
conveying a
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sheet having a leading end and a trailing end in a predetermined direction at
a first speed by a
first conveyer; detecting arrival of the sheet at a predetermined position of
the first conveyer;
transferring, by suction of a plurality of suction members arranged in said
predetermined
direction and activated simultaneously, the sheet in the entirety of a
dimension of the sheet as
measured in said predetermined direction from the first conveyer to a second
conveyer
disposed spaced vertically away from the first conveyer when the sheet has
arrived at said
predetermined position, and holding, by suction of said plurality of suction
members, the sheet
against the second conveyer, said second conveyer having a region overlapping
with the first
conveyer at least for a distance corresponding to said dimension of the sheet,
and said plurality
of suction members being disposed at least in said overlapping region of the
second conveyer
and operable to develop suction substantially over said entirety of the
dimension of the sheet;
conveying the sheet in said predetermined direction at a second speed by the
second conveyer;
and deactivating the suction of each suction member just after the trailing
end of the veneer
sheet has moved past said each suction member.
The second method comprises the steps of a method for conveying a series of
sheets,
comprising: conveying a sheet having a leading end and a trailing end in a
predetermined
direction at a first speed by a first conveyer; detecting arrival of the sheet
at a predetermined
position of the first conveyer; transferring, by suction of a plurality of
suction members, the
sheet in the entirety of a dimension of the sheet as measured in said
predetermined direction
from the first conveyer to a second conveyer disposed spaced above the first
conveyer when
the sheet has arrived at said predetermined position, and holding, by suction
of said plurality of
suction members, the sheet against the second conveyer, said second conveyer
having a region
overlapping with the first conveyer at least for a distance corresponding to
said dimension of
the sheet, and said plurality of suction members being disposed at least in
said overlapping
region of the second conveyer and operable to develop suction substantially
over said entirety
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of the dimension of the sheet; conveying the sheet in said predetermined
direction at a second
speed by the second conveyer; and deactivating the suction of each suction
member just after
the trailing end of the veneer sheet has moved past said each suction member.
According to some preferred embodiment, the second speed of the second
conveyer is
faster than the first speed of the first conveyer and the sheet is released by
a releasing
mechanism from the second conveyer at a predetermined releasing position by a
releasing
mechanism. The sheet thus released from the second conveyer is stacked onto a
pile of sheets.
In such a case, the releasing operation of the releasing mechanism is
completed before a next
sheet following the above sheet reaches the releasing position.
Features and advantages of the present invention will become more apparent to
those
skilled in the art from the following description of preferred embodiments of
the present
invention, which description is made with reference to the accompanying
drawings, wherein:
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CA 02648608 2009-01-09
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view showing a first embodiment of a sheet conveying
apparatus
according to the present invention;
FIG 2 is a rear view of the sheet conveying apparatus of FIG. 1 as viewed from
the
right-hand side of FIG. 1;
FIG. 3 is a partially sectional fragmentary view taken along and seen from
line Y-Y of
FIG 1;
FIGS. 4 through 7 are illustrative views showing different steps of operation
of the
sheet conveying apparatus of FIG 1;
FIG 8 is a side view showing a second embodiment of a sheet conveying
apparatus
according to the present invention;
FIG. 9 is a rear view of the sheet conveying apparatus of FIG. 8 as viewed
from the
right-hand side of FIG 8;
FIGS. 10 through 13 are illustrative views showing different steps of
operation of the
sheet conveying apparatus of FIG 8;
FIG. 14 is a side view showing a third embodiment of a sheet conveying
apparatus
according to the present invention;
FIGS. 15 and 16 are illustrative views showing different steps of operation of
the sheet
conveying apparatus of FIG. 14;
FIG. 17 is a side view showing a fourth embodiment of a sheet conveying
apparatus
according to the present invention;
FIGS. 18 through 22 are illustrative views showing different steps of
operation of the
sheet conveying apparatus of FIG 17;
FIG 23 is a side view showing a fifth embodiment of a sheet conveying
apparatus
according to the present invention;
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according to the present invention;
FIGS. 24 through 27 are illustrative views showing different steps of
operation of the
sheet conveying apparatus of FIG 23; and
FIG 28 is an illustrative view showing a veneer sheet conveying apparatus
according
to background art.
DETAILED DESCRIPTION OF EMBODIMENTS
The following will describe the first embodiment of the present invention with
reference to FIGS. 1 through 7.
The feature of the first embodiment resides in permitting a veneer sheet being
conveyed in a predetermined sheet conveying direction by a first conveyer to
be lifted or
transferred to a moving second conveyer without subjecting the veneer sheet to
a tension acting
in the sheet conveying direction and also making it possible to enlarge the
spacing between any
two adjacent veneer sheets in the conveying direction by moving the first and
second
conveyers at different conveying speeds.
Referring to the drawings, reference numeral 1 designates generally a first
conveyer
for conveying a series of veneer sheets 2g, 2h and so forth at a speed vl in
the arrow sheet
conveying direction. Referring to FIGS. 1 and 2, the first conveyer 1 include
a pair of spaced
rotary shafts 1 a (only one shaft being shown) spaced in the sheet conveying
direction and an
electric motor 1 e for constantly driving one of rotary shafts 1 a in arrow
direction. The first
conveyer 1 further includes two pairs of conveyer belts lc. The conveyer belts
lc of each pair
are spaced in the direction perpendicular to the sheet conveying direction,
wound between two
pulleys lb fixedly mounted on the rotary shafts 1a and traveling at the speed
v1. The two pairs
of conveyer belts l c are spaced in the direction perpendicular to the sheet
conveying direction.
A belt support Id is disposed immediately below the upper leg of the conveyer
belts lc. As
indicated by a chain line, the electric motor 1 e is operatively connected to
a control unit 8 of the
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Reference numeral 3 designates generally a second conveyer located above the
first
conveyer 1. Specifically, as shown in FIG 1, the second conveyer 3 is spaced
above the first
conveyer 1 at a spaced distance that is greater than the thickness of the
veneer sheet, e.g. 2g,
and overlaps on the upstream side thereof as viewed in the sheet conveying
direction with the
first conveyer 1 at least for a distance corresponding to the dimension of the
veneer sheet as
measured in the sheet conveying direction. For the sake of description, the
region of the
second conveyer 3 where it overlaps with the first conveyer 1 will be referred
to as S region
and the rest of the second conveyer 3 as T region, respectively, as indicated
by double-headed
arrows at the top of FIG. 1.
Referring specifically to FIGS. I and 2, the second conveyer 3 includes a pair
of
rotary shafts 3a spaced in the sheet conveying direction and an electric motor
3e for driving
constantly one of the rotary shafts 3a located on the downstream side or the
right-hand side as
seen in FIG 1. As best seen in FIG. 2, the second conveyer 3 further includes
two pairs of
conveyer belts 3c. The conveyer belts 3c of each pair, e.g. two conveyer belts
3c on the left
side as seen in FIG. 2, are spaced in the direction perpendicular to the sheet
conveying direction,
wound between two pulleys 3b fixedly mounted on the rotary shafts 3 a and
traveling at a speed
v2 that is faster than the speed vl. The two pairs of conveyer belts 3c are
spaced in the
direction perpendicular to the sheet conveying direction. As indicated by a
chain line, the
electric motor 3e is operatively connected to the control unit S.
Referring to FIGS. 1, 2 and 3, reference numeral 4 designates generally a
suction
mechanism for the second conveyer 3 including a pair of vacuum devices 4f of
multi-blade fan
type, an electric motor 4e connected to and driving each of the vacuum devices
4f, a closed
duct 4d connected also to each of the vacuum devices 4f. Each duct 4d is
disposed horizontally
above the second conveyer 3 and tapered so that the inner space of the duct is
reduced toward
the upstream end of the second conveyer 3 with respect to the sheet conveying
direction. The
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suction mechanism 4 further includes three suction members 4z provided for
each of the S and
T regions of the second conveyer 3. The suction members 4z are arranged
equidistantly along
the sheet conveying direction in each of the S and T regions of the second
conveyer 3 and
connected to the bottom of the duct 4d. Each suction member 4z has a
cylindrical connection
tube 4w connected to the duct 4d and a suction nozzle 4a connected to the
bottom of the
connection tube 4w and expanding downward. As indicated by a chain line, the
electric motor
4e is operatively connected to a control unit S.
As shown in FIG 3, the bottom of the suction nozzle 4a is perforated or formed
with a
plurality of suction holes 4h through which air is drawn into the suction
nozzle 4a, as will be
explained more in detail in later part hereof, and has at the opposite sides
thereof guide
projections 4g extending outward as seen in FIG. 3, i.e. in the direction
perpendicular to the
sheet conveying direction.
Referring to FIGS. 1 and 3, a disk-shaped valve 4b is fixedly mounted on a
rotatable
shaft 4j in each cylindrical connection tube 4w of the suction member 4z. The
valve 4b is
operable by an air cylinder 4c so as to open or close the air passage through
the cylindrical
connection tube 4w thereby to activate or deactivate suction vacuum at the
suction nozzle 4a.
As indicated by chain lines in FIG. 1, each air cylinder 4c is operatively
connected to the
control unit 8. As shown in FIG 3, the guide projections 4g of the suction
members 4z are
formed and arranged so as to guide the upper legs of the conveyer belts 3c of
the second
conveyer 3 in contact with the upper surface thereof.
The vacuum device 4f has a capacity to create suction vacuum in the closed
duct 4d
that is strong enough to lift a veneer sheet from the first conveyer 1 and
hold the veneer sheet
against the lower leg of the conveyer belts 3c of the second conveyer 3 by
suction developed in
the suction nozzle 4a. Three suction members 4z in each of the S and T regions
of the second
conveyer 3 are arranged so as to cover at least a distance that substantially
corresponds to the
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CA 02648608 2009-01-09
dimension of a veneer sheet as measured in the sheet conveying direction. That
is, the suction
members 4z in each of the S and T regions are arranged so as to activate
suction at least over
the above distance.
Referring to FIGS. 1 and 2 again, reference numeral 5 designates a sheet
releasing
mechanism provided in the T region of the second conveyer 3. The sheet
releasing mechanism
includes a pair of elongated releasing plates 5a for each pair of conveyer
belts 3c of the
second conveyer 3. The releasing plates 5 a of each pair are spaced away from
each other in the
direction perpendicular to the sheet conveying direction and extend in the
sheet conveying
direction. The sheet releasing mechanism 5 further includes an air cylinder 5b
for each
releasing plate Sa for vertically reciprocally moving the releasing plate 5a.
The air cylinders 5b
are connected to the control unit 8 and actuable to move the releasing plates
5a reciprocally for
the releasing operation of the releasing mechanism 5. Specifically, the
releasing plates 5a are
firstly moved downward to push a veneer sheet in the T region, e.g. 2f
indicated by solid line in
FIGS. 1 and 2, to a position that is close to a veneer sheet at the top of a
pile of veneer sheets 2A
stacked on a stacking plate 11 of a veneer sheet stacker of the apparatus,
which will be
described in detail later, and then moved upward back to their original
elevated position of FIG.
1. As will be described later, the air cylinders 5b are actuated for sheet
releasing operation each
time a veneer sheet being conveyed is located at a releasing position
immediately above a
veneer sheet stacking stand 10 of the stacker so that the veneer sheet is
released rapidly from
the second conveyer 3 and stacked onto the pile of veneer sheets 2A on the
stacking plate 11.
Reference numeral 6 in FIGS. 1 and 2 designates a first sheet sensor such as
photo cell
provided at a position adjacent to the downstream end of the first conveyer 1
and between the
two pairs of pulleys 3b and operatively connected to the control unit 8 as
indicated by chain
line in the drawings for detecting the leading end of an incoming veneer
sheet, such as 2g, and
generating a detection signal to the control unit S. That is, the first sheet
sensor 6 is disposed
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such that the leading end of the veneer sheet is detected by the sensor 6 when
the full sheet of
veneer has arrived in the S region of the second conveyer 3.
Reference numeral 7 designates a second sheet sensor of the same type as the
first
sensor 6, which is provided at an appropriate position adjacent to the
downstream end of the
second conveyer 3 for detecting the leading end of an incoming veneer sheet,
such as 2f,
conveyed by the second conveyer 3 and generating a detection signal to the
control unit 8. The
second sheet sensor 7 is disposed such that the leading end of veneer sheet is
detected by the
second sensor 7 when the veneer sheet has reached the veneer sheet releasing
position
immediately above the stacking stand 10.
Referring to FIGS. 1 and 3, reference numeral 50 designates a pair of rollers,
each
freely rotatably supported by a holder 51b mounted to the lower end of a
piston rod 51a of an
air cylinder 51 which is fixedly mounted to a frame (not shown) of the
apparatus. The roller 50
is reciprocally movable by the air cylinder 51 between the lowered position
with the piston rod
51 a fully extended out of the air cylinder 51, as indicated by solid line in
FIG. 1 and dotted line
in FIG. 3 and the elevated position with the piston rod 51a retracted in the
air cylinder 51, as
indicated by solid line in FIG. 3. The roller 50 in its lowered position is in
contact with the
upper surface of a veneer sheet being conveyed by the first conveyer 1 for
holding the veneer
sheet against the first conveyer 1, as shown in FIGS. 1 and also 5. On the
other hand, the roller
50 in its elevated position is spaced away from a veneer sheet which is then
held by suction
against the lower leg of the conveyer belts 3c of the second conveyer 3, as
shown in FIGS. 3
and also 4.
Referring to FIGS. 1 and 2, the aforementioned veneer stacking stand of the
stacker
designated generally by numeral 10 is provided below the T region of the
second conveyer 3
substantially corresponding to the aforementioned veneer sheet releasing
position and veneer
sheets conveyed by the second conveyer 3 to this position are released
successively from the
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second conveyer 3 and stacked one on another into a pile of veneer sheets on
this stacking
stand 10. The veneer sheet stacking stand 10 has a delivery conveyer l 0a. The
aforementioned
stacking plate 11 is placed on the delivery conveyer lOa for supporting
thereon a pile of veneer
sheets 2A. The veneer stacking stand 10 is operable to move vertically as
indicated by
double-headed arrow in FIGS. 1 so that the veneer sheet located at the top of
the pile 2A on the
plate 11 is kept at a predetermined level during the veneer sheet stacking
operation.
Controlling of such movement of the stacking stand 10 may be accomplished by
any suitable
control system known in the art.
The control unit 8 has incorporated therein a delay circuit and is operable to
receive
various signals from various devices and to control the operation of the sheet
conveying
apparatus as will be described in the following.
The following will describe the operation of the above-described veneer sheet
conveying apparatus according to the first embodiment with reference to FIGS.
1 and 4
through 7. The description of the operation will begin from the state of the
apparatus as
indicated by solid line shown in FIG. 1, wherein a plurality of veneer sheets,
such as 2h, 2g and
so forth, are being moved by the first conveyer 1 and a veneer sheet 2f held
by suction and
being conveyed by the second conveyer 3 by virtue of the friction acting on
the veneer sheet 2f
from the conveyer belts 3c is just about to reach the releasing position.
In the case of the present embodiment, as well as the other embodiments which
will be
explained hereinafter, all veneer sheets such as 2h, 2g, 2h and so forth have
substantially the
same length, width and thickness and each veneer sheet is conveyed in such an
orientation that
its length along the wood grain of the veneer sheets extend perpendicularly to
the veneer sheet
conveying direction and, therefore, each veneer sheet is conveyed with its
width moved along
the sheet conveying direction. That is, the lateral extension of a veneer
sheet as seen, e.g. in
FIG 1 corresponds to its width and the lateral extension of a veneer sheet as
seen, e.g. in FIG. 2
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correspond to its length.
For the sake of description, the following will deal with only full veneer
sheets each
having predetermined length and width. It is noted, however, that the present
invention is also
applicable to such a case wherein a plurality veneer strips having widths that
are short of the
predetermined width, but the sum of such short widths makes the full width, is
dealt with as a
full sheet.
In the state in FIG. 1, the valves 4b in the cylindrical connection tubes 4w
of three
suction members 4z for the T region of the second conveyer 3 are opened, so
that a veneer
sheet 2f is held by suction against the lower leg of the conveyer belts 3c of
the second conveyer
3. By virtue of the friction between the veneer sheet 2f and the conveyer
belts 3c, the veneer
sheet 2f thus held against the conveyer belts 3c is moved by the conveyer 3.
On the other hand,
the valves 4b of three suction members 4z for the S region of the second
conveyer 3 are closed,
so that a veneer sheet 2g is being moved by the first conveyer 1. As shown in
FIG 1, a plurality
of veneer sheets 2g, 2h and so forth are being conveyed by the first conveyer
1 with very little
spacing between any two adjacent veneer sheets.
When the veneer sheet 2f is moved further by the second conveyer 3 to reach
the
releasing position immediately above the stacking stand 10 of the stacker, the
leading end of
the veneer sheet 2f is detected by the second sheet sensor 7, which then
generates a detection
signal to the control unit 8. The control unit 8 receiving such detection
signal from the second
sensor 7 actuates simultaneously the air cylinders 4c of the suction members
4z for the T region
of the second conveyer 3 so as to close their corresponding valves 4b
simultaneously thereby to
deactivate suction at the suction nozzle 4a. Simultaneously, the control unit
8 also actuates the
air cylinders 5b so as to reciprocate the releasing plates 5a of the sheet
releasing mechanism 5.
As a result, the veneer sheet 2f is released from the conveyer belts 3c of the
second conveyer 3,
as shown in FIG 4, and dropped onto the top of the pile of veneer sheets 2A.
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In the meantime, the veneer sheet 2g following the veneer sheet 2f is conveyed
at the
speed v 1 by the first conveyer 1 toward the S region of the second conveyer
3, as shown in FIG.
1. When the leading end of the veneer sheet 2g is detected by the first sheet
sensor 6, the
control unit 8 receiving a detection signal from the first sensor 6 actuates
simultaneously the air
cylinders 4c of the suction members 4z for the S region of the second conveyer
3 so as to open
their valves 4b simultaneously, thereby activating suction at the suction
nozzle 4a for the S
region. Simultaneously, the control unit 8 actuates the air cylinders 51 so as
to retract their
piston rods 51 a into the cylinders 51 thereby to shift the rollers 50 to
their elevated position. As
a result, the veneer sheet 2g is lifted or transferred from the first conveyer
1 to the second
conveyer 3 and held by suction against the lower legs of the conveyer belts 3c
of the second
conveyer 3 by suction developed in the suction nozzles 4a of the suction
members 4a for the S
region of the second conveyer 3, as shown by solid line in FIG 4. In this
transferring, the
suction of the suction nozzles 4a of three suction members 4z for the S region
acts substantially
on the entire width of the veneer sheet 2g, the lifting is accomplished for
the entire width of the
veneer sheet 2g.
The veneer sheet 2g thus transferred from the first conveyer 1 is further
moved in the
sheet conveying direction by the second conveyer 3 then at the speed v2 that
is faster than vI.
Accordingly, the veneer sheet 2g is accelerated by receiving frictional force
from the second
conveyer 3 acting in the sheet conveying direction. When the veneer sheet 2g
is accelerated,
frictional force of the second conveyer 3 acts on the entire veneer sheet 2g,
so that the veneer
sheet 2g is subjected to no tension acting in the sheet conveying direction,
with the result that
the veneer sheet 2g is conveyed forward safely without being broken.
Receiving the above detection signal from the first sensor 6, the control unit
8
performs various controlling operations. In response to the detection signal,
the control unit 8
generates a series of command signals through its incorporated delay circuit
to actuate the air
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CA 02648608 2009-01-09
cylinders 4c of the suction members 4z for the S region of the second conveyer
3. Specifically,
the command signals are generated successively with such delays that the air
cylinders 4c for
the S region are successively actuated so as to close their valves 4b thereby
to deactivate
suction at each of the suction nozzles 4a just after the trailing end of the
veneer sheet 2g has
moved past each of such suction nozzle 4a. Such operation of the valves 4b in
synchronism
with the movement of a veneer sheet is performed to ensure stability in
conveying of veneer
sheet by the second conveyer 3. That is, if the valve 4b at any suction member
4z kept open
even after the trailing end of the veneer sheet has moved past its
corresponding suction nozzle
4a, a large amount of air is drawn through the suction holes 4h into the
suction members 4z and,
therefore, suction vacuum in the duct 4d is decreased significantly.. This
lowers the suction at
the suction nozzles 4a under which the veneer sheet is held against the belt
conveyers 3c, with
the result that the veneer sheet may fail to be conveyed properly or be
dropped off from the
second conveyer 3.
In response to the above detection signal from the first sensor 6, the control
unit 8 also
generates a command signal with such a delay that the air cylinders 51 are
actuated so as to
move the rollers 50 to their lowered position into contact with the upper
surface of the
subsequent veneer sheet 2h for holding it against the first conveyer 1, as
shown in FIG. 5, after
the trailing end of its preceding veneer sheet 2g has moved past the rollers
50 and also the
leading end of the veneer sheet 2h has reached below the rollers 50. By so
controlling, the
veneer sheet 2h being conveyed by the first conveyer 1 is prevented from being
lifted by
suction then acting in the suction nozzle 4a provided at the upstream end of
the S region of the
second conveyer 3, i.e. the leftmost suction nozzle 4a as seen, e.g. in FIG.
5.
Furthermore, the control unit 8 receiving the above detection signal from the
first
sensor 6 generates a series of command signals successively through its
incorporated delay
circuit to actuate the air cylinders 4c of the suction members 4z for the T
region of the second
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conveyer 3 with such delays that the air cylinders 4c for the T region are
successively actuated
to so as to open their valves 4b thereby to activate suction at each of the
suction nozzles 4a just
before the leading end of the veneer sheet 2g reaches each of such suction
nozzle 4a, as
appreciated from FIGS. 5 and 6. Such operation of the valves 4b for the T
region of the second
conveyer 3 in synchronism with the movement of a veneer sheet is performed for
the same
purpose of ensuring stability in conveying a veneer sheet by the second
conveyer 3.
Thus, the veneer sheet 2g is moved by the second conveyer 3 toward the
releasing
position immediately above the veneer sheet stacking stand 10, as shown in
FIGS. 5 through 7.
When the leading end of the moving veneer sheet 2g is detected by the second
sensor 7, the air
cylinders 5b are actuated to activate the releasing plates 5a of the sheet
releasing mechanism 5
for separating the veneer sheet 2g from the conveyer belts 3c of the second
conveyer 3 and
allowing the sheet 2g to be dropped onto the top of the pile of veneer sheets
2A in the same
manner as in the case with the preceding veneer sheet 2f.
A veneer sheet 2h following the veneer sheet 2g and conveyed by the first
conveyer 1
is lifted and transferred to the second conveyer 3 in the same manner as in
the case of its
preceding veneer sheet 2g when the leading end is detected by the first sheet
sensor 6, and
conveyer further at the speed v2 by the second conveyer 3 in the same manner
as described
above with the case of the veneer sheet 2g.
For accomplishing smooth and uninterrupted stacking of veneer sheets at the
stacking
station, the conveying speeds vI and v2 of the first and second conveyers 1
and 3 and the time
required for the releasing plates 5a to make a complete reciprocating
operation are so
established that releasing of the veneer sheet 2g from the second conveyer 3
is completed
before the next veneer sheet 2h reaches the releasing position. The spaced
distance between
any two adjacent veneer sheets, e.g. veneer sheets 2g and 2h, on the second
conveyer 3 can be
figured out by multiplying the difference between v2 and vl by the length of
time from the
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moment when the veneer sheet 2g begins to be conveyed by the second conveyer 3
until the
next veneer sheet 2h begins to be conveyed by the second conveyer 3.
The above-described steps of operation are repeated to convey and stack a
series of
veneer sheets successively. According to the embodiment, veneer sheets being
conveyed by
the first conveyer 1 with very little spacing between any two adjacent veneer
sheets can be
stacked uninterruptedly by transferring them to the second conveyer 3 running
faster than the
first conveyer 1. As obvious from the foregoing, a veneer sheet being moved by
the first
conveyer 1 is lifted or transferred by suction in its entirety along the width
thereof extending in
the sheet conveying direction. That is, a veneer sheet being moved by the
first conveyer 1 at
the speed vl receives in its entire width the frictional force from the second
conveyer 3. Thus,
according to the present embodiment, the veneer sheet is subjected to no
damaging tension
acting in the sheet conveying direction and the spacing between any two
adjacent veneer sheets
can be enlarged without braking the veneer sheets.
The following will describe the second embodiment of the present invention
with
reference to FIGS. 8 through 13. In the following description, those parts or
elements which
are similar to the counterparts of the first embodiment will de designated by
like numerals or
symbols and the details description of such parts and elements will be
omitted. The feature of
the second embodiment is substantially the same as that of the first
embodiment.
The sheet conveying apparatus of the second embodiment has substantially the
same
first conveyer 1 having the conveyer belts lc traveling at the speed vl as the
first conveyer of
the first embodiment. The second embodiment differs from the first embodiment
in that the
second conveyer 3 of the first embodiment having pairs of conveyer belts 3c
each extending
over the S and T regions is substituted by a second conveyer 9 having separate
conveyer belts
9c and 9h for the S and T regions, respectively, and also that the sheet
releasing mechanism 5 of
the first embodiment is dispensed with.
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Referring to FIG. 8, the second conveyer 9 includes an upstream conveyer 9A
and a
downstream conveyer 9B connected together in series in the sheet conveying
direction. The
upstream conveyer 9A has a pair of spaced rotary shafts 9a, pulleys 9b mounted
on the rotary
shafts 9a, two pairs of conveyer belts 9c installed between two pulleys 9b and
an electric motor
9e for driving constantly the rotary shaft 9a located on the right-hand side
as seen in FIG. 1.
The upstream conveyer 9A is disposed spaced above the first conveyer 1 at a
distance that is
greater than the thickness of the veneer sheet, overlapping with the first
conveyer 1 at least for
a distance corresponding to the widthwise dimension of a veneer sheet, e.g. 2t
(FIG. 8) as
measured in the sheet conveying direction and spaced upward from. The range of
the upstream
conveyer 9A which overlaps with the first conveyer 1 for the above distance
forms the S region,
as indicated by double-headed arrow at the top of FIG 1. The upstream conveyer
9A of the
second conveyer 9 is driven to travel constantly at the speed v2 that is
faster than the speed vl
of the first conveyer 1.
Referring to FIGS. 8 and 9, the downstream conveyer 9B has a rotary shaft 9f,
pulleys
9g fixedly mounted on the rotary shafts 9a, 9f, two pairs of conveyer belts 9h
installed between
the pulleys 9g and an electric motor 9j operable to drive and stop the rotary
shaft 9f as required.
The downstream conveyer 9B forms the T region of the second conveyer 9. The
stacking stand
10 of the stacker is located below the downstream conveyer 9B.
Unlike the electric motor 9e, the electric motor 9j for the downstream
conveyer 9B is
operable to be activated or deactivated (or stopped) as required in response
to a command
signal from the control unit 8A, so that the conveyer belts 9h of the
downstream conveyer 9B is
operated accordingly. To permit such operation of the downstream conveyer 9B,
the
downstream pulley 9g of the paired pulleys 9g is freely rotatably mounted on
the rotary shaft
9a.
The suction mechanism 4 and its relates parts and devices are constructed and
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arranged substantially in the same manner as the counterparts of the first
embodiment. The
same is true of the paired rollers 50 and the control unit 8A. The first and
second sheet sensors
6 and 7 are located at appropriate positions adjacent to the downstream ends
of the first
conveyer 1 and the downstream conveyer 9B of the second conveyer 9,
respectively.
The following will describe the operation of the veneer sheet conveying
apparatus of
the second embodiment. The description of the operation will begin from the
state of the
apparatus shown in FIG. 8, wherein the valves 4b of three suction members 4z
for the T region
are all opened and a veneer sheet 2s is held by suction against and being
moved by the
conveyer belts 9h of the downstream conveyer 9B. The valves 4b of three
suction members 4z
for the S region are all closed. As in the case of the first embodiment, a
plurality of veneer
sheets such as 2t and 2u are being moved the first conveyer 1.
When the veneer sheet 2s is moved further by the downstream conveyer 9B of the
second conveyer 9 to reach the releasing position immediately above the
stacking stand 10, the
leading end of the veneer sheet 2f is detected by the second sheet sensor 7,
which then
generates a detection signal to the control unit 8A. The control unit 8A
receiving such
detection signal deactivates the electric motor 9j thereby to stop the
downstream conveyer 9B
and then actuates the air cylinders 4c of the suction members 4z for the T
region of the second
conveyer 9, so that their corresponding valves 4b are closed simultaneously
for deactivating
the suction at the suction nozzles 4a of these suction members 4z. As a
result, the veneer sheet
2s is released and dropped by its own weight from the conveyer belts 9h onto
the top of the
veneer sheet pile 2A.
In the meantime, the veneer sheet 2t following the veneer sheet 2s is conveyed
at the
speed vl by the first conveyer 1 toward the S region of the upstream conveyer
9A, as shown in
FIG. 8. When the leading end of the veneer sheet 2t is detected by the first
sheet sensor 6, the
control unit 8A actuates simultaneously the air cylinders 4c of the suction
members 4z for the S
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region and also the air cylinders 51 for the rollers 50 in the same manner as
in the first
embodiment, with the result that the veneer sheet 2t is lifted in its entire
width and held by
suction against the conveyer belts 9c of the upstream conveyer 9A and conveyed
at the speed
v2 in arrow sheet conveying direction, as shown in FIG. 10.
The control unit 8A receiving the above detection signal from the first sensor
6
generates a series of command signals successively through its incorporated
delay circuit.
Specifically, the command signals are generated by the control unit 8A to
start the electric
motor 9j for driving the downstream conveyer 9B and also to actuate the
cylinders 4c of the
suction members 4z for the S region and the T region so as to close valves 4b
for the S region
and to open the valves 4b for the T region in synchronism with the movement of
the veneer
sheet 2t as described in detail with reference to the first embodiment for
ensuring stability in
conveying the veneer sheet by the second conveyer 9. Thus, the veneer sheet 2t
is conveyed
toward the releasing position immediately above the stacking stand 10, as
shown in FIGS. 11
through 13. When the leading end of the veneer sheet 2t is detected by the
second sheet sensor
7, the conveyer belts 9h are stopped, which is immediately followed by
deactivation of suction
at the suction nozzles 4a for the T region. As a result, the veneer sheet 2t
is dropped by its own
weight from the downstream conveyer 9B of the second conveyer 9 onto the top
of the veneer
sheet pile 2A.
Though the description of the rollers 50 has been omitted, they are operated
in
substantially the same manner as the counterparts of the first embodiment.
The above-described steps of operation are repeated to convey and stack a
series
veneer sheets successively. As obvious from the foregoing, this second
embodiment offers the
same effects as the first embodiment.
In the first embodiment, a veneer sheet being conveyed by the second conveyer
3 is
released therefrom positively by using the releasing mechanism 5 and stacked
onto a veneer
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sheet pile 2A. In such an arrangement, the error in the position in the sheet
conveying direction
at which veneer sheets are released is large, as a result of which veneer
sheets fail to be stacked
into a neat pile due to their displacement relative to stacking position. This
will make
troublesome the subsequent veneer sheet handling operation. In the second
embodiment
according to which each veneer sheet moved by the downstream conveyer 9B is
stopped before
it is released, however, the aforementioned error and hence the displacement
of veneer sheets
can be reduced.
Though the second embodiment dispenses with the veneer sheet releasing
mechanism
such as 9 of the first embodiment, however, the use of the releasing mechanism
positively
releasing the veneer sheet from a conveyer belt is advantageous in that veneer
sheet releasing
can be done rapidly and the time required for stacking a given number of
veneer sheets be
reduced, accordingly.
The following will describe the third embodiment of the present invention with
reference to FIGS. 14 through 16.
The sheet conveying apparatus of the third embodiment has substantially the
same
first conveyer 1 having the conveyer belts 1 c traveling at the speed v 1 as
the first conveyer of
the first and second embodiments. The third embodiment differs from the first
embodiment in
that the second conveyer 3 of the first embodiment is substituted by a second
conveyer 12
which is constructed shorter than the second conveyer 3. Accordingly, the
closed duct 4t of the
suction mechanism 4A is made shorter as compared with the duct 4d of the first
embodiment.
As shown in FIG 14, four suction members 4z are connected to the duct 4d. The
second
conveyer 12 is spaced above the first conveyer 1 at a distance that is greater
than the thickness
of the veneer sheet and disposed overlapping with the first conveyer 1 at
least for a distance
corresponding to the width of a veneer sheet, e.g. 2y (FIG. 14) as measured in
the sheet
conveying direction. The second conveyer 12 has conveyer belts 12c (only one
belt being
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shown) wound between the pulleys 12b fixedly mounted on the rotary shafts 12a
one of which
is driven by the electric motor 3e. As in the first embodiment, the conveyer
belts 12c of the
second conveyer 12 are driven constantly to travel at the speed v2 that is
faster than the speed
vl of the conveyer belts lc of the first conveyer 1.
The sheet conveying apparatus of the third embodiment also differs from the
first
embodiment in that the stacker is dispensed with and a third conveyer 13 is
provided instead at
a position below the second conveyer 12 and adjacent to the downstream ends of
the first
conveyer 1 and the second conveyer 12. The third conveyer 13 includes a
conveyer belt 13c
wound between a pair of pulleys 13b (only one pulley being shown in the
drawing) fixedly
mounted on a pair of shafts 13a (only one shaft being shown) one of which is
driven by an
electric motor (not shown) for driving the conveyer belt 13c at the speed v2.
As shown in FIG.
14, the third conveyer 13 is provided overlapping with the second conveyer 12
over a short
distance and spaced from the second conveyer 12 at a spaced distance that is
slightly greater
than the thickness of a veneer sheet. The paired rollers 50 and the control
unit 8B are
substantially the same as the counterparts of the first embodiment. The
apparatus includes the
control unit 8B and the first sheet sensor 6, dispenses with the second sheet
sensor 7.
The following will describe the operation of the veneer sheet conveying
apparatus of
the third embodiment. The description of the operation will begin from the
state of the
apparatus as shown in FIG. 14, wherein the valves 4b of the first three
suction members 4z as
counted from the upstream end of the second conveyer 12 are closed and a
veneer sheet 2x
being conveyed by the second conveyer 12 with its trailing end held by suction
of the fourth
suction member 4z whose valve 4b is opened is being transferred from the first
conveyer 1 to
the third conveyer 13. A plurality of veneer sheets 2y, 2z and so forth are
being conveyed by
the first conveyer 1.
When the veneer sheet 2y is moved further by the first conveyer 1 to reach the
position
CA 02648608 2009-01-09
where its leading end is detected by the first sheet sensor 6, a detection
signal is transmitted
from the first sensor 6 to the control unit 8B. The control unit 8 receiving
such detection signal
actuates simultaneously the air cylinders 4c of the above three suction
members 4z so as to
open their corresponding valves 4b thereby to activate suction at such suction
members 4z. As
a result, the veneer sheet 2y is lifted in its entire width and held by
suction against the conveyer
belts 12c of the second conveyer 12, as shown in FIG. 15. The control unit 8B
actuates the air
cylinder 4c of the fourth suction member 4z so as to close its valve at such a
time when
substantially the entire veneer sheet 2x has been transferred to the third
conveyer 13.
The veneer sheet 2y thus lifted from the first conveyer 1 is then conveyed at
the faster
speed v2 by the second conveyer 12. Further, the control unit 8B provides a
command signal
with a delay to actuate the air cylinder 4c for the fourth suction member 4z
so as to open its
valve 4b just before the leading end of the veneer sheet 2y reaches the
suction nozzle 4a of that
fourth suction member 4z and also a series of signals to actuate the air
cylinders 4c so as to
close the valves 4b in synchronism with the movement of the veneer sheet 2y
for the reason
stated earlier herein.
In the meantime, the veneer sheet 2y held against the conveyer belts 12c of
the second
conveyer 12 enters a region between the lower leg of the conveyer belts 12 of
the second
conveyer and the upper leg of the conveyer belt 13c of the third conveyer 13,
as shown in FIG
16, and moved further as its preceding veneer sheet 2x.
As is obvious from the foregoing, veneer sheets being transferred from the
first
conveyer 1 to the second conveyer 12 are subjected to no damaging tension
acting in the sheet
conveying direction and the spaced distance between any two adjacent veneer
sheets being
conveyed can be enlarged without braking the veneer sheets.
The following will describe the fourth embodiment of the present invention
with
reference to FIGS. 17 through 22.
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The feature of the fourth embodiment resides in that selected veneer sheets
out of a
series of veneer sheets conveyed by the first conveyer are continued to be
moved by the first
conveyer without being transferred to the second conveyer. In the fourth
embodiment, it is so
arranged that every other sheet continues to be conveyed by the first
conveyer.
Referring to FIG. 17, the first conveyer 1 includes the conveyer belts 1c
driven to
travel at the speed vl and a sloped extension conveyer 14 having conveyer
belts 13a one end of
which is wound around the pulley 1b. The first sheet sensor 6 is provided for
detecting the
leading end of an incoming veneer sheet such as 2k moved by the conveyer belts
lc of the first
conveyer 1. The sloped conveyer belts 14a of the sloped extension conveyer 14
is inclined
downward from the pulley lb and traveling at the same speed vl as the conveyer
belts lc. A
third sheet sensor 15 is located adjacently to the upper leg of the sloped
conveyer belt 14a at a
position spaced from the first sheet sensor 6 at a distance that substantially
corresponds to the
width of a veneer sheet 2k as measured in the sheet conveying direction.
The second conveyer 17 of the fourth embodiment has the same pairs of conveyer
belts 12c as the counterparts belts 3c of the first embodiment, drive to
travel constantly
between the pulleys 12b mounted on the rotary shafts 12a at the speed vl in
arrow direction.
The second sheet sensor 1 S is provided at a position adjacent to the
downstream end of the
second conveyer 17 for detecting the leading end of a veneer sheet being moved
by the second
conveyer 17. A suction mechanism 4B having seven suction members 4z is
provided for the
second conveyer 17 in the same manner as in the first embodiment, although
vacuum devices
4f and the closed ducts 4d are omitted from the drawing for the sake of
clarity of illustration.
For the sake of description, the second conveyer 17 is divided into three
regions S, U and W.
Namely, the range covering the first three suction members 4z as counted from
the upstream
end of the second conveyer 17 with respect to the sheet conveying direction
will be referred to
as S region, the range covering fourth suction member 4z as U region, and the
range covering
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CA 02648608 2009-01-09
the last three suction members 4z as W region, respectively.
A third delivery conveyer 19 is arranged below the W region of the second
conveyer
17, having a conveyer belt running constantly at the speed vl. The paired
rollers 50 (only one
roller being shown) are arranged substantially in the same manner as the
counterparts of the
first embodiment. Though not shown in the drawing, a control unit is provided
for controlling
the operation of the valves 4b of the respective suction members 4z and the
roller 50 in
response to signals from the sheet sensors 6, 15, 18, as will be described
later.
The following will describe the operation of the veneer sheet conveying
apparatus of
the fourth embodiment. The description of the operation will begin from the
state of the
apparatus as shown in FIG 17, wherein the valves 4b of the suctions members 4z
for three
regions S, U and W are all closed and a plurality of veneer sheets 2k, 2m and
so forth are being
conveyed by the first conveyer 1. The veneer sheet 2k on the first conveyer 1
has just reached
a position where its leading end is detected by the first sheet sensor 6.
When the first sheet sensor 6 detects the leading end of the incoming veneer
sheet 2k,
the control unit (not shown) provides command signals to actuate
simultaneously the air
cylinders 4c for three suction members 4z for the region S so as to open their
valves 4b. The
veneer sheet 2k is lifted and held by suction against the conveyer belts 12c
of the second
conveyer 12, as shown in FIG 18, and then conveyed forward in arrow direction
at the speed
vl. As described earlier with reference to the foregoing embodiments, for
ensuring stability in
conveying of veneer sheet, the operation of the valves 4b to open and close is
controlled by the
control unit in conjunction with the movement of the veneer sheet 2k.
In the mean time, the veneer sheet 2k is further moved by the second conveyer
17 to a
position where its leading end is detected by the second sensor 18, as shown
in FIG 19. In the
state of FIG 19, the valves 4b of the suction members 4z for the regions S and
U of the second
conveyer 17 are all closed. The control unit responding to a detection signal
from the sensor 18
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CA 02648608 2009-01-09
actuates the air cylinders 4c of the suction members 4z for the region W of
the second conveyer
17 so as to close their valves 4b simultaneously. Therefore, the veneer sheet
2k is released
from the second conveyer 17 and dropped off by its own weight from the
conveyer belts 12c of
the second conveyer 17 onto the third delivery conveyer 19, as shown in FIG.
20, and conveyed
further by the third delivery conveyer 19 at the same speed vl to any
subsequent working
station outside the apparatus.
In the case of the veneer sheet 2m following the sheet 2k, when its leading
end is
detected by the first sheet sensor 6, no signal is generated for actuating the
air cylinders 4c so as
to open the valves 4b of the suction members z for the region S of the second
conveyer 17.
Therefore, th veneer sheet 2m is transferred to the sloped extension conveyer
14, as shown in
FIG. 19 without being lifted to the second conveyer 17. The veneer sheet 2m is
followed by a
veneer sheet 2n.
When the leading end of the veneer sheet 2m moved by the sloped extension
conveyer
14 is detected by the third sheet sensor 15, the control unit receiving a
detection signal from the
sensor 15 generates signals to actuate the air cylinders 4c of the suction
members 4z for the S
region so as to open their valve 4b simultaneously. The veneer sheet 2n is
lifted and held by
suction against the conveyer belts 12c of the second conveyer 12, as shown in
FIG 21, and
moved forward in arrow direction at the speed vl in the same manner as the
veneer sheet 2k.
When the veneer sheet 2n is conveyed by the second conveyer 17 to a position
as shown in FIG
22, it is released and dropped onto the third delivery conveyer 19 and moved
at the speed vl to
the subsequent station outside the apparatus in the manner as described with
reference to the
preceding veneer sheet 2k.
The above-described steps of operation are repeated to convey a series of
veneer
sheets alternately to two different conveying passages, namely the sloped
extension conveyer
14 of the first conveyer 1 and the third delivery conveyer 19.
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The sheet conveying apparatus of this embodiment may use a veneer sheet
releasing
mechanism such as 5 having releasing plates 5a of the first embodiment for
positively releasing
veneer sheets from the second conveyer 17.
The following will describe the fifth embodiment of the present invention with
reference to FIGS. 23 through 27.
The sheet conveying apparatus of this fifth embodiment differs from the
foregoing
embodiments in that the second conveyer to which a veneer sheet is transferred
is disposed
spaced below the first conveyer. Accordingly, a veneer sheet being conveyed by
the first
conveyer is supported thereby with the upper surface of the veneer sheet held
by suction
against the first conveyer and then transferred by being dropped to the second
conveyer.
Referring to FIG. 23, reference numeral 20 designates a first conveyer having
two
pairs of conveyer belts 21c (only one belt being shown in the drawing)
provided in a similar
arrangement to the case of conveyer belts 3c of the second conveyer 3 of the
first embodiment
(FIG. 2) and wound between the pulleys 21c fixed mounted on the rotary shafts
21a, each
running at the speed v1 in arrow direction. A first sheet sensor 22 is located
at a position
adjacent to the downstream end of the second conveyer 21 for detecting the
leading end of an
incoming veneer sheet such as 2k conveyed by the first conveyer 20. A suction
mechanism 4C
having a plurality of suction members 4z is provided for the first conveyer
20, although
vacuum devices 4f and their associated parts such as closed ducts 4d are
omitted from the
drawing for the sake of clarity of illustration.
Reference numeral 2' designates a second conveyer disposed below the first
conveyer
20 and having a region overlapping therewith for a distance that is slightly
greater than the
width of a veneer sheet as measured in the sheet conveying direction. The
second conveyer 23
has pairs of conveyer belts 24c (only one conveyer belt being shown in the
drawing) driven to
travel constantly between the pulleys 24b fixedly mounted on the rotary shafts
24a at the speed
-27-
CA 02648608 2009-01-09
v2 in arrow direction. A suction mechanism 4D having four suction members 4z
is provided
for the second conveyer 23, although vacuum devices 4f and their associated
closed ducts 4d
are omitted from the drawing. As shown in FIG. 23, the suction members 4z of
the suction
mechanism 4D are disposed with the suction nozzles 4a facing upward in contact
with the
lower surfaces of the upper leg of the conveyer belts 24c. The first three
suction members 4z as
counted from the upstream end of the second conveyer 23 are arranged in the
above
overlapping region corresponding to the distance that is slightly greater than
the width of a
veneer sheet and the fourth suction member 4z is located downstream of the
third suction
member 4z. A second sheet sensor 27 is located at an appropriate position for
detecting the
leading end of a veneer sheet being conveyed by the second conveyer 23.
Reference numeral 25 designates a third conveyer disposed adjacently to and
substantially in alignment with the first conveyer 20 and overlapping with the
second conveyer
23 at least over a distance that is larger than the width of a veneer sheet as
measured in the sheet
conveying direction. Like the first conveyer 20, the third conveyer 23 has two
pair of conveyer
belts 26c (only one conveyer belt being shown) driven to travel constantly
between the pulleys
26b mounted on the rotary shafts 26a at the speed v2 in arrow direction. A
suction mechanism
4E having a plurality of suction members 4z is provided for the third conveyer
25, although
vacuum devices 4f and their associated closed ducts 4d are omitted from the
drawing.
Though not shown in the drawing, a control unit is provided which receives
detection
signals from the first and second sheet sensors 22, 27 and controls the
operation of the veneer
sheet conveying apparatus. The apparatus of this embodiment dispenses with the
rollers 50.
The following will describe the operation of the veneer sheet conveying
apparatus of
the fifth embodiment. The description of the operation will begin from the
state of the
apparatus as shown in FIG. 23, wherein the valves 4b of the suctions members
4z for the first
conveyer 20 are all opened to hold by suction veneer sheets such as 2k, 2m, 2n
and so forth
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CA 02648608 2009-01-09
against the conveyer belts 21c of the first conveyer 20, while the valves 4b
of the suction
members 4z for the second conveyer 23 and the third conveyer 25 are all
closed.
When the leading end of a veneer sheet 2k being conveyed by the first conveyer
20 is
detected by the first sensor 22, the control unit (not shown) provides command
signals to
actuate the air cylinders 4c of those three suction members 4z for the first
conveyer 20 which
are located adjacent to the pulley 2lb at the downstream end of the first
conveyer 20 so as to
close their valves 4b simultaneously and also to actuate the air cylinders 4c
of the suction
members 4z for the second conveyer 23 so as to be open their valve 4b, as
shown in FIG. 24.
As a result, the veneer sheet 2k is released or transferred from the first
conveyer 20 to the first
conveyer 23. In the transferring, the veneer sheet 2k is move also by
attraction by suction of
the suction mechanism 4D to the second conveyer 23. That is, the veneer sheet
2k is
transferred to the second conveyer 23 by its own weight, as well as by suction
acting to move
the veneer sheet 2k downward. Thus, the veneer sheet 2k is held by suction
against the moving
conveyer belts 24c of the second conveyer 23, as shown in FIG. 24, so that the
veneer sheet 2k
is conveyed in arrow direction at the speed v2, as shown in FIG. 25. The
valves 4b of the
suction members 4z for the second conveyer 23 are closed successively in
conjunction with the
movement of the veneer sheet 2k for ensuring stability and smoothness in
conveying of veneer
sheets.
After elapse of a short period of time from the time of reception of the
detection signal
from the first sheet sensor 22, i.e. after the veneer sheet 2k has been
transferred to and held by
suction against the second conveyer 23, the control unit generates a series of
command signals
to actuate the air cylinders 4c of the aforementioned three suction members 4z
for the first
conveyer 20 so as to open their valves 4b successively in conjunction with the
conveying
movement of the next veneer sheet 2m. When the leading end of the veneer sheet
2m is
detected by the first sensor 22, the veneer sheet 2m is transferred to the
second conveyer 23,
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CA 02648608 2009-01-09
held against its conveyer belts 24c and conveyed in the sheet conveying
direction at the speed
v2 in the same manner as its preceding veneer sheet 2k, as shown in FIG. 26.
Because of the
difference of conveying speed between the first and second conveyers 20 and
23, a spaced
distance is formed between the two adjacent veneer sheets 2k, 2m being
conveyed by the
second conveyer 23, as shown in FIG 26.
In the mean time, when the leading end of the veneer sheet 2k being moved by
the
second conveyer 23 is detected by the second sheet sensor 27, the control unit
causes the air
cylinders 4c of three suction members 4z (shown in FIG 25) for the third
conveyer 25 to be
actuated so as to open their valves 4b simultaneously. As a result, the veneer
sheet 2k is lifted
and held by suction against the conveyer belts 26c of the third conveyer 25
and conveyed in
arrow direction at the speed v2, as shown in FIG. 27. Similarly, the following
veneer sheets 2m,
2n and so forth are conveyed at the speed v2 by the third conveyer 25 with a
spacing formed
between the trailing and leading ends of any two adjacent veneer sheets.
Though not shown in any of the drawings, a stacking station and veneer sheet
releasing mechanism such as those which are used in the first embodiment may
be provided at
any suitable downstream region of the third conveyer 25 having three suction
members such as
those suction members 4z show, e.g., in FIG 26. In such a case, veneer sheets
conveyed by the
third conveyer 25 are successively stacked onto a veneer sheet pile by
deactivating suction at
the suctions nozzles 4a of such suction members 4z and simultaneously
activating the releasing
mechanism in the same manner as in the first embodiment.
As a matter of course, the third conveyer 25 may be dispensed with and veneer
sheets
conveyed by the second conveyer 23 with a spacing between any two adjacent
veneer sheets
may be stacked at any stacking station provided adjacently to the downstream
end of the
second conveyer by using any know sheet stacker. For example, the sheet
conveying apparatus
may use a stacker having a pair of sheet supporting bars spaced away from each
other in the
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CA 02648608 2009-01-09
direction perpendicular to the sheet conveying direction and adapted to
receive thereon veneer
sheets successively and then to release them byrmoving the bars away from each
other thereby
to allow a veneer sheet to be released and dropped onto a veneer sheet pile.
As is apparent from the foregoing, no damaging tension acts on a veneer sheet
when it
is transferred from the first conveyer 20 to the second conveyer 23 and also
from the second
conveyer 23 to the third conveyer 25.
It is to be understood that the present invention can be practiced in various
changes
and modifications as exemplified below without departing the spirit of the
present invention.
In lifting a veneer sheet by suction of the suction members 4z from the first
conveyer
to the second conveyer in the first through fourth embodiments, the lifting
may be assisted by
air blown against the entire lower surface of the veneer sheet from below. For
example, in the
case of the first embodiment, a blower duct may be provided below the upper
leg of the
conveyer belts lc of the first conveyer 1 so that air blowing acts over the
entire width of a
veneer sheet. Air blowing may be activated synchronously with the opening of
the valves 4b
of the suction members 4z for the S region of the second conveyer 3. The use
of such blower
helps to shorten the time for a veneer sheet to be transferred to the second
conveyer.
The first sheet sensor 6 for detecting the arrival of a veneer sheet at a
predetermined
position in the S region, e.g. in the first embodiment, is located at a
position adjacent to the
downstream end of the first conveyer 1, although detection of the veneer sheet
may be done at
any suitable position upstream of the above end of the first conveyer 1. In
such a case,
determination of the arrival of a veneer sheet at a position where it is to be
lifted for
transferring may be accomplished by counting the moving distance of the belt
conveyer lc
from the point of detection by using any suitable pulse counter.
In the first through fifth embodiments, the vertical spaced distance between
two
conveyer belts of any two conveyers disposed one above the other, for which a
veneer sheet is
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CA 02648608 2009-01-09
moved by suction for transferring, may be set as desired depending on various
factors such as
capacity of the vacuum device, weight of a veneer sheet, etc.
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