Note: Descriptions are shown in the official language in which they were submitted.
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BOARD INVERTER FOR LUMBER CONVEYOR
FIELD OF THE INVIENTION
The present invention relates to sawmill equipment. In particular, it relates
to lumber
conveyancing within a mill, wherein boards are inverted about their long axis
while being
conveyed across a board grading table or other processing station, to expose
the underside
of the board for grading and other purposes.
BACKGROUND OF 'THE INVENTION
Designers of modern higlh speed lumber mills seek to automate lumber handling,
in order to
enhance accuracy, increase speed and reduce repetitive strain injuries amongst
workers. One
of these repetitive steps is the rotation of boards, along their long axis, as
they are carried
along a lumber convc;yor. For example, a board grading table typically
includes
conveyancing means, whereby boards are conveyed along the length of the table,
in a
direction transverse to the long axis of the board. Conveniently, the boards
may be inverted
partway along the table, to expose the underside of the board to permit an
inspection to be
carried out on all sides of the board. Other board conveyancing operations
also require
periodic inversion of boards as the same are conveyed either between lumber
processing
stations, or within a lumber processing station.
The present invention operates in the context of a lumber conveyor wherein
individual,
spaced apart boards are conveyed from one end of the conveyor to the other,
with the
boards being arranged transversely to their direction of movement. A board
rotator of the
type characterized by the present invention may be situated part way along the
conveyor,
whereby the boards are inverted by 180° along their long axis by the
action of the rotator.
Turning to the prior art, U.S. patent 3,247,963 (Fehely) discloses a pivotally
mounted arm
which contacts a lower face of a board as the same as conveyed along a
conveyor. Rotation
of the arm engages the board, lifts the same upwardly from the table and
carnes the board
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forwardly in an arc, whereby the board lands back on to the conveyor inverted
180° from
its starting position. An array of arms is shown mounted to a common shaft,
for engaging
a board at several positions along its length. The boards are conveyed along
the conveyor
by a continuous chain or belt, having a series of upright lugs which contact a
trailing face of
each board. The common shaft is rotatably driven, conveniently by a cogged
engagement
with the main conveyor chain. The Fehely device requires that the boards be
precisely
spaced in order to properly engage the rotators. Thus, any mis-positioning of
the boards on
the conveyor or slippage of the conveyor relative to the chain, will disrupt
the timing of the
rotator and hamper its .ability to properly rotate the boards. It is desirable
to provide an
alternative means for rotating boards along a conveyor. In particular, it is
desirable to
provide a rotator which does not require precision coordination of the board
movement with
the rotary action of the :rotator.
SUMMARY OF THE INVENTION
The present invention comprises in one aspect a board inverter for use in
association
with a lumber conveyor, of the type comprising a frame and conveyor means
supported on
said frame for carrying lumber boards along said frame transverse to their
direction of travel
along said frame. The inverter comprises a central hub freely rotatable about
an axle for
mounting to said frame, and at least one arm extending from said hub, said arm
including a
recessed portion adapted to receive and releasably retain a lower face of said
board and to
rotate the board relative to the transport means as said boards are conveyed.
Preferably, the inverter has at least four, evenly-spaced arms, each arm being
providexi with a leading f ice and a trailing face relative to the direction
of movement of said
arm, said recessed portion being recessed into said trailing face, wherein
each of said boards
is adapted to be engaged between said leading face of a first arm and the
recessed portion
of an adjacent second arm.
In another aspect, the invention comprises a lumber conveyor comprising in
combination, a board inverter as defined above, said inverter being rotatably
mounted to the
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frame of said lumber conveyor, whereby said at least one arm extends upwardly
above the
plane of said conveyor 'when said arm is positioned vertically upwardly.
In another aspect, there is provided at least two of said board inverters
mounted to
said frame, in spaced apart positions whereby the hubs of said inverters are
coaxial, and the
arms of said inverters may simultaneously contact a board conveyed through
said transport
means.
In another aspect, the lumber conveyor further includes an array of board
engagement lugs fastened to said conveyor means for extending upwardly
therefrom, each
of said lugs having a generally concave forward face having an upper portion
sloping
relatively steeply, said forward face adapted to contact said boards to convey
said boards
forwardly while elevating; a portion of said board as a leading edge board
contacts said board
inverter, whereby said lugs and at least one inverter cooperate to rotate said
boards.
The conveyor means may comprise a continuous chain, with an array of said lugs
being fastened to the chain. Preferably, there are provided multiple spaced
apart parallel
conveyor means, each of said conveyor means having fastened thereto an array
of said lugs
arranged to generally simultaneously contact a board conveyed.
In another aspect, the invention consists of a lug, for use with the above
arrangements. The lug has a leading face which is generally concave and plough-
shaped
when viewed in side elevation, wherein a lower portion of said lug slopes
upwardly and
rearwardly in a relatively shallow angle, merging with an upper portion
sloping upwardly at
a relatively steep angle, said lug being configured to contact a trailing face
of a board
conveyed through said conveyor, and elevate said trailing face of said board
as a leading
portion of said board contacts said board inverter.
The invention fi.~rther comprises one or more lugs of the above description,
in
combination with one or more inverters of the above description.
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In another aspect, the invention is a method for inverting boards as they are
conveyed through a lumber processing station. This aspect comprises the steps
of
A method for inverting a board within a lumber processing station, comprising
the
steps of
a) providing a lumber conveyor for conveying a board transversely to the long
axis of the board;
b) providing an array of lugs associated with said conveyor engaging said
board, s~~id lugs each having a generally concave leading face;
c) providing; a board inverter comprising a freely rotatable hub mounted to
said
conveyor and an array of evenly spaced arms extending radially from said
hub, each arm having a recess therein in its trailing edge to receive and
releasably retain a board therein;
d) engaging a board with said lugs and conveying a board along said conveyor;
e) engaging; a board between said recess of a first of said arms and a leading
face of a second of said arms wherein contact with said moving board causes
rotation of said inverter;
f) rotating acid board by means of said inverter and depositing said board on
a downstream side of said inverter in an inverted position.
Preferably, the inverter is continuously rotated by contact and engagement
with an
array of boards evenly spaced on said conveyor.
Having thus generally described and summarized the invention, the invention
will
now be characterized by a detailed description of a preferred embodiment of
the invention
and accompanying drawings.
BRIEF DESCRIPTIO:IV OF THE DRAWINGS
Figure 1 is a perspective view of a lumber grading station incorporating the
present
invention, showing for clarity the chain drive and lugs removed;
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Figure 2 is a front elevational view of the grading station of Figure 1;
Figure 3 is a side elevational view of a portion of the device, illustrating
the board
rotating element of the apparatus;
Figure 4 is a side elevational view of a board engagement lug; and
Figure 5 is a side elevational view of the board inverter element.
DETAILED DESCRIIPTION OF THE PREFERRED EMBODIMENT
A lumber grading station 100, which incorporates the invention, is illustrated
schematically
at Figures 1 and 2. Lumber processed by the station is taken up at an upstream
end, with
the lumber being transported in a transverse position through the device and
scanned therein,
to a downstream end of the device. After infeed into the station 100, each
board receives
an initial scan by a first bank of scanners 80 of its upper and forward
lateral faces. The
board is then rotated at>out its longitudinal axis by 180 °, following
which its previously
unscanned faces, namely the upper and forward lateral faces, are scanned by a
second bank
of scanners. The board is then delivered from the device to various downstream
processing
means, including trim saws, sorter and stampers for indicating the grade of
the board.
The grading station 100 is supported by a frame 1, having a pair of forward
vertical supports
2(a) and a pair of rearwa~~d vertical supports 2(b), each pair being
positioned inboard of the
ends of the device. A horizontal cross beam 3 links the tops of opposing
vertical support
members. An elongate grading table 4 extends the length of the device,
extending between
opposing pairs of vertical support members 2. The grading table is comprised
of an array
of longitudinal beams S, comprising a central beam 5(a) and lateral beams S(b)
and (c) on
either side thereof, linked at their ends to transverse beams 6 and each
supported by legs 7.
The lateral beams 5(b) and (c) are fixed to the support members 2 by means of
links 8.
A chain guide 10, comprising a U-shaped channel, is mounted to the top of each
beam S and
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extends the length thereof., The chain guide is fabricated out of ultra high
molecular weight
nylon, or other abrasion-resistant material having a low friction coefficient.
A chain sprocket 20, shown in Figure 2, is mounted to each end of each
longitudinal beam,
rotatably engaged to a support bracket 21 that links the sprocket to a
corresponding end of
a beam S. Drive chains 22(a), (b) and (c), respectively, are looped
longitudinally around the
beams 5(a), (b) and (c), slidably engaged within each chain guide 10 and are
engaged by the
chain sprockets 20. The central drive chain 22(b) is driven by an electric
motor 23. The
motor 23 may be positioned on the floor under the device, as illustrated, or
may be
suspended from the central beam. 'the motor is linked to the drive chain 22(b)
by means of
a belt 24, engaged to a drive sprocket 25 mounted to the central chain
sprocket 20 adjacent
the motor 23. The speed of the motor is infinitely variable and is controlled
by the control
and information processing means, described below. The lumber transport means
is adapted
to transport lumber through the device at speeds of up to 240 boards per
minute.
Referring to Figure 3, individual boards 26 fed through the device are engaged
by an array
of lugs 30, each lug being engaged to a corresponding drive chain and
extending upwardly
therefrom when the chain is positioned within chain guide 10. Each board has
an upper face
27, a lower face 28, and forward and rearward lateral faces 29(a) and (b),
respectively. The
directional references refer to a board in its initial infeed position, as
shown in the left side
of Figure 5. Each lug is engaged to a corresponding chain by way of a pair of
mounting
plates 31 positioned on either side of each lug and engaged to a link of the
chain. The lugs
are spaced at regular intervals of between 18 and 36 inches along the length
of each chain,
with the chains being positioned within the device such that lugs engaged to
the chains
22(a), (b) and (c) describe a series of even rows across the width of the
grading table.
Refernng to Figure 4, each lug 30 has generally flat sides 33; a horizontal
base 34 and top
35; and leading and trailing faces 40 and 41, respectively. When positioned
within the chain
guide, the leading face of the lug faces the front of the device. The leading
face has a
generally plow-shaped concave profile when viewed from the side, with a lower
portion 42
sloping upwardly and rearwardly at a relatively shallow angle relative to the
base, merging
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with a slightly curved, generally vertical upper portion 43, having a slight
forward lean at its
upper end. The configuration of the forward face is adapted to retain a board
driven across
the grading table, and to cooperate with a board inverter, described below, to
rotate the
board about its longitudinal axis. The configuration of the trailing face does
not affect the
operation of the device.
Referring to Figures 3 and 4, board inverters 50 are mounted to at least one
of the beams
5, intermediate between the forward and rearward vertical supports 2(a) and
2(b). The
board inverters are adapted to rotate each boaxd 26 by 180 ° about its
longitudinal axis.
Where the device is adapted for use with longer length boards, longer than 12
feet, two or
more inverters may be provided. When shorter length boards are processed, only
a single
inverter is required. The board inverter 50 comprises a generally planar
structure, freely
rotatable about a centr,~l axis 51 mounted to a beam 5, having four arms 52
extending
radially outwardly at right angles from each other. Each arm has a generally
flat top 53, a
leading face 54 and a trailing face 55, relative to the normal direction of
rotation thereof.
The leading face 54 is generally flat, and is perpendicular to the
longitudinal axis of the
adjacent pair of arms. The trailing face has a recessed lower portion 60 and
an upper
portion 61 that slopes upwardly and rearwardly when viewed with the arm
extending
upwardly.
As each board is pushed iPorwardly through the device by the lugs 30, its
forward face 29(a)
contacts the recessed portion 60 of an upwardly-extending first arm and is
loosely engaged
therein. The lower face 28 of the board contacts the leading face 54 of a
second adjacent
arm. As the board continues its forward movement, driven by the lugs 30, the
forward
motion of the board pivola the inverter about its axis, as shown in the dotted
lines of Figure
3, lifting and rotating the board. Continued forward movement of the board
causes the
inverter to rotate the board by 180 ° and deposit the inverted board on
the forward side of
the inverter. The sloping configuration of the forward face of the lugs
cooperated with the
action of the inverter to smoothly rotate each board.
It will be seen that an array of regularly spaced boards conveyed sequentially
by the
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lugs, and sequentially engaging the inverter, will cause the inverter to
continuously rotate.
It will be obvious to those having ordinary skill in the art that variations
to the preferred
embodiments described above may be made without departing from the spirit and
scope of
the invention, as defined by the appended claims.
