Note: Descriptions are shown in the official language in which they were submitted.
CA 02577656 2013-08-30
ALIGNING LUG LOADER
Field of the Invention
This invention relates to an apparatus for the singulation or allocation of
lumber into lug spaces on a lugged transfer, or other lumber conveying device,
and in
particular relates to an apparatus capable of collecting, singulating,
straightening, allocating
and consistently spacing, rough sawn lumber or planed finished lumber, or
sticks of varying
widths, thickness and lengths into consecutive spaced-apart lugs, or allocated
spacings onto a
transfer, or lugged transfer, or to a stick placing device, at high speeds.
Background of the Invention
Conventional lug loaders or singulators (hereinafter collectively referred to
as
either lug loaders or singulators) have been found to be inadequate at higher
feed speeds.
They are also limited in their ability to both singulate and allocate lumber.
When lumber is
of varying widths and varying in thickness, or bowed, as may be predominant in
curve
sawing mills, cupped or crooked, and/or skewed on the transfer, it becomes
increasingly
difficult to handle the lumber at desirable higher speeds.
An example of a conventional lug loader is that taught in U.S. Patent No.
3,923,142 which issued to Rysti on December 2, 1975. In particular, what is
being taught is
singulating boards by use of supporting arms rotating around a closed loop,
the orientation of
the supporting arms controlled by curved deflectors. Pressing arms in opposed
radial pairs,
are rotatably mounted above the supporting arm to synchronously clamp a board
onto a
supporting arm. Downstream
flow of the mat of boards is arrested by a stop on each supporting arm. Rysti
does not
disclose a mechanism for straightening lumber which is skewed on the infeed
transfer in the
lug loader.
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Applicants are also aware of U.S. Patent No. 5,518,106, which issued to Allard
on
May 21, 1996. Allard discloses using fixed pick-up shoes mounted onto rotating
discs for
engaging and supporting boards being singulated. Fixed shoes however, have the
disadvantage
that they may mark the underside of the board as the board is translated over
the top of the disc and
as the board is released. If a board is finished, for example destined for
cabinet making or the like,
then any marks from the shoe or overhead clamp will reduce the value of the
board. Allard also
discloses a speed-up belt to pull the board away from the fixed shoes at the
top of the disc to
prevent the board from being flipped over as the board is released from the
shoes. In some mills
the boards have been marked for trimming and grading before the lug loader.
Thus if the board
has been flipped over by the singulator, as may occur in the case of the
Allard device, the board
must be flipped back by hand to read the mark. This can be difficult in a high
speed application.
Many lug loaders in the prior art, particularly those operating at slower feed
speed,
require that, in order to stop the delivery of boards to the singulator, the
board mat moving
downstream into the singulator device must be pushed back upstream by the
stopping means, that
is forced away from, for example, the fixed pick-up shoe and clamping device.
Worse yet, in
some prior art devices the board delivery mechanism must be brought to a
complete stop. Both
pushing the mat of boards back upstream, and stopping the board delivery
mechanism, can be
impractical at high speed.
In the prior art applicant is also aware of U.S. Patent Nos. 5,921,376 and
6,199,683
which issued to Michell et al for, respectively, a High Speed Revolving Lug
Loader With
Retracting Heel and Hook and a High Speed Revolving Board Singulator With
Retracting Shoe
and Variable Dwell Duckers, both of which describe the mechanical manipulation
of boards to
load the boards into individual lug spaces in a lugged outfeed transfer.
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Applicant is also aware of the following U.S. Patent Nos. in the prior art
relating to
the present invention: 4,077,524; 4,144,976; 4,330,055; 4,638,440; 4,869,360;
5,419,425;
5,662,203; and 5,813,512.
Summary of the Invention
The proposed invention is a transfer system. The transfer system makes use of
conveyors such as chains or belts to move lumber pieces downstream while
oriented traversely
across the flow path. The lumber pieces enter the virtual lug loading system
according to the
present invention moving transversely. The lumber pieces may enter as a
tightly spaced sheet or
mat of pieces with no gaps, or the lumber pieces may be randomly spaced and
oriented.
Within the system a first grouping of transfers create consistent gaps between
individual lumber pieces. The speed with which the lumber pieces are
translated downstream is
varied to create spaces between the lumber pieces. The first group of
transfers may be driven
individually or ganged together. In one embodiment individual transfers or
pairs of transfers are
selectively and independently actuable to vary their speeds so that the gaps
may be created, for
example, by increasing the velocity of successive transfers in the downstream
direction.
The transfers in the second grouping of transfers are individually driven.
They
maintain the gapping, that is the spacing between lumber pieces, and allow a
surge capacity.
Being individually driven, these transfers also provide for skew correction
should the lumber
pieces arrive skewed or skew during a transition from one transfer to another.
These transfers gap
and straighten the pieces as required so that one piece is positioned into
each lug space on
downstream lugged transfer chains. Thus, individually driven belts within this
second grouping of
transfers provide skew correction to correct the orientation of skewed lumber
pieces on the infeed
to the lugged transfer being loaded. Keeping the lumber pieces straight, that
is oriented traversely
across the flow path on the infeed, helps deal the lumber pieces into the lug
spaces.
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Dealing the boards directly into lug spaces without a mechanical lug loader
simplifies the loading of the lug spaces in the lugged transfer as compared to
the prior art. It
improves operator access, and reduces the amount of mechanical components
requiring
maintenance.
In one aspect of the present invention, servo controlled decks singulate the
lumber
pieces and position them directly into a lugged chain.
In summary the virtual lug loader according to one aspect of the present
invention
includes a lug loader for loading workpieces in a flow direction into the
spaced apart lugs on a
lugged conveyor, wherein the workpieces are transversely oriented relative to
the flow direction.
The lug loader includes an array of pairs of endless conveyors for conveying
the workpieces
downstream, wherein each pair of endless conveyors in the array include first
and second endless
conveyors. The first and second endless conveyors are spaced laterally apart
across the flow
direction. Each are aligned substantially in the flow direction. The array
forms a continuous upper
surface in the flow direction for supporting the workpieces translating
downstream in the flow
direction. Each pair of endless conveyors in the array overlap adjacent pairs
of endless conveyors
in the array. At least one pair of endless conveyors in the array include
independently actuable
first and second drives independently driving their corresponding first and
second endless
conveyors.
When a skewed workpiece, that is one which is skewed from its transverse
orientation, is translating on the first and second endless conveyors, the
first or second drive
corresponding to one of the pair of endless conveyors advances the upstream-
most end of the
workpiece relative to its downstream-most end to correct the workpiece to an
un-skewed position
oriented transversely to the flow direction.
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The array may include an upstream gapping section and a downstream lug loading
section. Advantageously, the first and second endless conveyors, that is the
pair or pairs of
conveyors which are independently actuable so as to correctly orient skewed
workpieces, is or are
found within the lug loading section. However, it is not intended as limiting
the scope of the
present invention to have only gapping sections followed by skew correction
sections. It is
intended that in the present invention also to interleaf gapping sections with
skew correction pairs.
Further, skew correction could be done anywhere within the transfer system
instead ofjust the lug
loading section.
The pairs of endless conveyors in the gapping section may translate the
workpieces
in the flow direction at increasing downstream velocities between an upstream
end of the gapping
section and a downstream end of the gapping section. The increasing downstream
velocities may
be successively increasing downstream velocities corresponding to successive
pairs of endless
conveyors between the upstream and downstream ends of the gapping section.
The number or proportion of endless conveyors either overall to the system, or
within the lug loading section, which are the independently actuable pairs of
endless conveyors
may be for example, not intended to be limiting, substantially half of the
number of pairs of
endless conveyors.
The independently actuable pairs of endless conveyors each have corresponding
selectively actuable drives so that each of those pairs of endless conveyors
is asymmetrically
actuable to drive one endless conveyor ahead of another endless conveyor to
correct skew of a
workpiece on any one of those endless conveyors.
The adjacent pairs of endless conveyors in the array may overlap at adjacent
ends
thereof by one endless conveyor of the adjacent pairs being inset laterally
across the flow direction
relative to a corresponding second endless conveyor of the adjacent pairs.
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The present invention also is intended to include within its ambit a method of
virtual lug loading corresponding substantially to the use of the above
described apparatus.
Brief Description of the Drawings
Figure 1 is a side elevation view of the virtual lug loader according to the
present
invention shown in an elongated view having component views in Figures 1A, 1B
and 1C intended
to be viewed side-by-side in sequence.
Figure 2 is a plan view of the virtual lug loader of Figure 1 shown in an
elongated
view having component views in Figures 2A, 2B and 2C intended to be viewed
side-by-side in
sequence.
Figure 3 is the lug loader of Figure 2 showing, diagrammatically, sensors and
controls.
DetailedDescription of Embodiments of the Invention
As seen in the accompanying figures wherein similar characters of reference
denote
corresponding parts in each view, the Virtual Lug Loader according to the
present invention
includes a gapping section 10 immediately upstream, relative to a direction of
flow A, of lug
loading section 12. Workpieces 14 arrive in direction A so as to form a mat or
blanket 16 of
workpieces 14 on infeed transfer 18. Workpieces 14 arriving at the upstream
end of infeed
transfer 18 may be fed from, for example, a tilt hoist, a landing table, an
unscrambler, or other
wood handling machinery.
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Mat 16 is formed on infeed transfer 18 as the workpieces are slowed on
transfer
belts 20. At the downstream end of infeed transfer 18, workpieces 14 are urged
onto the upstream
ends 22a of a first pair of belts 22 for progressively faster translation of
each workpiece 14 in
direction A as the workpieces are transferred from the downstream end of
infeed transfer 18 onto
sequentially and progressively faster successive pairs of belts 22, 24, 26,
28, and 30 within
gapping section 10. Gapping section 10 may, alternatively, may be thought of
as a lumber
separation zone. Thus, a workpiece 14 having a velocity Vo in direction A on
infeed transfer 18,
will, once handed off to the first pair of belts 22, have a downstream
velocity V1, and then
sequentially increasing velocities V2, V3, V4, V5 thereby sequentially
increasing the separation
between individual work pieces 14 by reason of the progressive acceleration of
the boards between
pairs of belts.
Advantageously, the separation between individual workpieces 14 is increased
as
the length of the gaps, distance g between adjacent workpieces is increased
for example to
approximately one hundred twenty-five per cent of the length of each lug
space, distance I,
between lugs 32a of lugged outfeed chains 32. It is understood that, although
five pairs of belts
22-30 are illustrated, it is not intended to limit the present invention to
five pairs of belts in
gapping section 10 as more or fewer pairs of belts will suffice so long as
sequential workpieces 14
are separated in direction A so that gap distance g is at least equal to lug
space distance 1.
The pairs of belts 22, 24, 26, 28 and 30 in gapping section 10 may each be
driven
by variable frequency drives or induction motors 34 along with associated gear
heads. In the
illustrated example, not intended to be limiting, each of the five speed-up
zones corresponding to
the five belt pairs are approximately sixteen inches long so that the length
in the downstream
direction of gapping section 10 is approximately six foot, eight inches.
In a preferred embodiment, lug loading section 12 is immediately downstream,
and
cooperates with, the downstream end of gapping section 10 so that workpieces
14 are smoothly
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handed off from belts 30, being the downstream most pair of belts in gapping
section 10, to the
first pair of control zone belts 36 located immediately downstream of the
interface B between
gapping section 10 and lug loading section 12. Lug loading section 12 is a
workpiece control zone
wherein skew may be corrected such as the skew of a workpiece 14' illustrated
in dotted outline on
control zone belts 38. Skew correction is accomplished by each belt in each
pair of control zone
belts 36, 38, 40, 42, 44, and 46 being able and adapted to selectively operate
at different speeds. In
order to correct skew, for example a skew angle alpha (a) of a skewed
workpiece 14' the two belts
38, and subsequent downstream belts as need be, are driven at different speeds
relative to one
another as board 14' passes over the belts, so that the lagging end of the
boar catches up with the
advanced end of the board until the board is correctly positioned
perpendicularly across the
direction of flow A.
Apart from operating to correct the skew of workpieces translating downstream
in
direction A, the independently actuable control zone belts in the belt pairs
of lug loading section
12 also, in addition to those belts in gapping section 10, operate to
selectively space the boards
apart and synchronize the boards with upcoming lugs 32a as the lugged outfeed
chains 32 rotate in
direction C. Thus the control zone belts are driven by a motion controller
(not shown) to
accelerate or decelerate pairs of belts 36, 48, 40, 42, 44 and 46 to
simultaneously accelerate or
decelerate both belts in individual pairs of belts so as to accelerate or
decelerate a workpiece which
has been corrected for a skew. This is done to synchronize and match the
placement of a particular
workpiece into, for example, the middle of a corresponding lug space as the
workpiece exits the
downstream end of lug loading section 12. Thus as may be seen, the
acceleration or deceleration
of the sequence of workpieces 14 being translated downstream over the
sequential array of pairs of
belts 38, 40, 42, 44 and 46, are selectively motion controlled so as to place
a workpiece 14
entering onto the upstream end of the lugged outfeed chains 32 preferably into
for example the
middle of a corresponding lug space or otherwise exiting off the downstream
end of belts 46 just
after a pair of lugs 32a rotate to the vertical as chains 32 rotate endlessly
around sprockets 48.
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In the illustrated embodiment, not intended to be limiting, lug loading
section 12 has
six control zone belt pairs may be thought of as six belt modules each
approximately sixteen
inches long in the downstream direction for a total downstream length of eight
feet. In one
preferred embodiment, the motors 50 which selectively individually drive each
belt in each
belt module, may be servo motors having corresponding gear heads.
It is understood that sensors 52 such as seen in Figure 3 and known in the
prior
art, and as would be known to one skilled in the art, would be provided to
detect the position
of individual boards and that the information from the sensors is processed by
a digital
processor 54 cooperating with the sensors and that the digital processors also
cooperates with
a programmable logic controller (PLC) 56 via network 58 which in turn
cooperates with the
motors for selectively driving the belts 22, 24, 26, 28 and 30 in gapping
section 10 and belts
36, 38, 40, 42, 44 and 46 in lug loading section 12.
In interpreting both the specification and the claims, all terms should be
interpreted in the broadest possible manner consistent with the context. In
particular, the
terms "comprises" and "comprising" should be interpreted as referring to
elements,
components, or steps in a non-exclusive manner, indicating that the referenced
elements,
components, or steps maybe present, or utilized, or combined with other
elements,
components, or steps that are not expressly referenced.
As will be apparent to those skilled in the art in the light of the foregoing
disclosure, many alterations and modifications are possible in the practice of
this invention.
Accordingly, the scope of the invention is
to be construed in accordance with the substance defined by the following
claims.
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