Note: Descriptions are shown in the official language in which they were submitted.
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METAL CUTTING PROCESS
FIELD OF THE INVENTION
This invention relates to the cutting of metal sheets, such as for example,
steel plates
used in heavy metal fabrication.
BACKGROUND OF THE INVENTION
In heavy metal fabrication industries, it is often required to cut large
sheets of
metal, typically steel, to a given profile according to a particular design.
These sheets
may be too large and too heavy for convenient manipulation by hand. In the
past,
complex patterns were scribed, drawn in chalk or painted on the metal sheet to
be cut.
Personnel would then, typically, use torches to cut the desired profile as
laid out. This
system had a number of disadvantages, most notably the reliance on human skill
both for
transferring the design to the metal sheet, and in making the cut.
More recently, metal plates have been mounted on supports and moved beneath a
bridge or gantry having a movable cutting head. The combination of being able
to move
the bridge on rolling supports in one direction, while being able to move the
cutting head
across the span of the bridge in a perpendicular direction permitted a profile
of arbitrary
planar shapes to be cut as desired. The addition of programmable control
increased both
the accuracy and productivity of the cutting process, and the use of a plasma
arc cutting
head permits the cuts to be made with higher accuracy than with a flame
cutting torch.
In particular, plasma arc cutting has been used with the work piece to be cut
supported on a submerged bed located in a bath. The bath is thought to absorb
or reduce
the noxious fumes produced in the cutting process. When the cut is finished,
the liquid
level in the bath is reduced to expose the parts, the cut parts are removed,
and new
materials are added.
However, while there may have been a significant investment in the cutting
machinery, and in the controls used to operate the cutting machinery, the
portion of the
duty cycle spent in the cutting operation remained relatively low. For
example, in the
first step the supporting frame would be loaded with large sheets to be cut.
This loading
process generally involved using cranes to lift new sheets from a stock of
sheets, carrying
the sheets overhead, and carefully placing the new sheets to be cut in
position.
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Once the sheets were in position, the level of liquid in the bath was raised
again to
submerge the material. The cutting apparatus could then cut the sheet into the
desired
pieces. When finished, the cutting head would be moved to one side to give
access to the
various pieces. The shop personnel would then transport the cut pieces to the
next
production stage (or inventory, as might be), and remove the scrap. Removal of
cut
pieces did not tend to occur while other cutting was underway, since it might
not have
been prudent for personnel accidentally to provide an unintentional path to
ground for the
plasma arc, loading generally requires the lowering of the liquid level in the
bath, and a
mistake in moving material could result in shifting the remaining pieces to be
cut, thus
possibly yielding an incorrect profile. For these reasons it was generally
only practical to
remove pieces after cutting was complete.
Unloading commenced with the lowering of the level of the bath. Once all of
the
useful pieces and scrap had been moved away, the new stock could be brought
in, and the
table re-loaded. Typically, the removal of cut pieces and scrap impeded the
placement of
new sheets on the cutting frame such that removal had to be complete before
the laying of
new sheets for cutting could begin. Once loaded with new material, the level
of the bath
would be raised again to immerse the new sheets. All the while, during loading
of new
stock and unloading of cut pieces and scrap, the cutting machinery tended to
be idle. By
one estimate, the length of time spent loading and unloading significantly
exceeded the
actual time spent cutting. Although it was possible to improve production by
operating
two baths end-to-end, sharing a cutting head, the overall level of
productivity was not
necessarily entirely satisfactory. It would be advantageous to cut material
more nearly
continuously, and to permit at least some of the unloading of cut parts to
occur in a
different location, from the loading of new sheets of metal.
The baths had another disadvantage related to operation in cooler climates.
Although sheltered from wind and snow, the shop was typically not heated. If
the bath
were left inoperative for a significant length of time, such as during
Christmas shut-down,
either a heating element was required to keep the bath above freezing, or anti-
freeze was
required, or both. Antifreeze would have to be drained, and the bath flushed
before re-
commencing operation. If the bath were allowed to freeze, the time and effort
required to
put the system back in operation was significant.
In still more recent times, plasma arc systems have been operated without
using
the submerged bath apparatus. Rather than using a liquid medium to absorb
undesirable
gases, a vacuum system is used to draw off the gases. Not using a bath system
provides
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the opportunity to unload and reload the work material not piece-by-piece,
while the
cutting heads sit idle, but rather by changing out the entire bed. That is, by
having several
beds, and moving them relatively quickly, the entire cutting facility can be
re-loaded in a
few minutes, and then loading and unloading can take place elsewhere while the
material
in the next bed is cut. When a non-liquid bath system is used, it is possible
to move an
entire bed more easily, without concerns about managing the liquid in the
bath. The beds
can be moved either by lifting, as with overhead gantry cranes, or by movement
along a
track work, such as might be laid on the floor of a bay.
In the former process, parts were removed piece-by-piece, using
electromagnetic
clamps to lift the cut pieces of steel. (in the case of non-magnetic materials
magnetic
lifting is not appropriate, in which case other lifting techniques, such as
suction systems
can be used in some instances). It would be advantageous to lift all the
pieces off the bed
at once, or in a relatively small number (two or three) of lifts, then to
carry them away
with an overhead crane, or to lay then on pallets where other equipment, such
as forklifts
and tractors, can sort and transport the cut parts as need be. It is similarly
advantageous
to be able to re-load the beds in a position away from the cutting head, or
heads. By
doing this, a vacant bed can more quickly be made ready for another cutting
operation.
Use of a bath to submerge the material to be cut tended also to impose
practical
limitations on the size of pieces that could be cut. Part size was limited by
the bath size.
When a particularly large panel was desired a number of individual plates
would have to
be cut, aligned, and butt-welded together. For example, a number of different
types of
rail road cars employ side walls that are of the order of 60 ft in length, and
up to about 11
feet in width from side sill to top chord. An example of such a car is a grain
car or a
plastic pellet car. These sidewalls have generally been fabricated by joining
a plurality of
plates together. It would be advantageous to be able to accept sheet from the
rolling mill
in a sufficient length and width to be able to cut these side walls from a
single sheet,
thereby eliminating the fabrication involved in butt-welding a number of
plates together.
Such a method of fabrication would tend to reduce defects in the resultant car
structure,
would tend to reduce tolerance build-up in the overall assembly, and generally
facilitate
assembly of the cars.
At present, long steel sheet, such as would be required to make a single piece
side
sheet of 60 ft length is available in coils from the rolling mill. To process
the sheet
directly, the coils require uncoiling. Consequently, it would be advantageous
to provide a
de-coiling facility adjacent to the cutting facility. It would also be
advantageous to be
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able to load the uncoiled sheet directly into a cutting bed, and then move the
bed into
position for cutting.
SUMMARY OF THE INVENTION
The invention relates to an apparatus for cutting sheet metal, in which there
is a
cutting head that is operable to cut profiles in two dimensions, such as an x-
y plane in
generally planar work pieces, such as metal sheet or plate. The apparatus also
includes
movable carriages, or beds, on which the work piece material is loaded. The
beds are
movable such that once a bed is loaded, it can be relatively quickly moved
into a cutting
position under the cutting tool, by which it can be cut. Once cutting is
complete, the first
movable bed can be moved away relatively quickly, and another movable bed can
take its
place in the cutting position, whereby the productivity of the cutting process
may tend to be
enhanced by keeping the cutting head busy while the first, and other,
carriages are being
unloaded and loaded (or re-loaded).
In one aspect of the invention there is an apparatus for the cutting of sheets
of metal
material. The apparatus has a first transfer carriage for supporting material
to be cut, a
cutting head, and a pathway along which to move the transfer carriage. The
cutting head
and the transfer carriage are movable relative to each other to permit the
cutting head to
cut profiles of objects lying in a plane. The carriage is movable between a
loading
position clear of the cutting head, and a cutting position in which the camage
presents the
material to be cut to the cutting head. The pathway has a portion along which
the carriage
can by-pass the cutting head.
In a feature of that aspect of the invention, motion of the cutting head
relative to
the transfer carriage is automatically controlled. In another feature of that
aspect of the
invention, the cutting head includes a cutting member chosen from the set of
cutting
members consisting of (a) a cutting torch; and (b) a plasma arc. In an
additional feature,
the apparatus further includes a venting system operable to convey fumes from
operation
of the cutting member away from said apparatus. In another feature, the
venting system is
a vacuum system operable to draw fumes from below the cutting head.
In another feature, at least the cutting head and a portion of the path
adjacent to
the cutting head are mounted within a sheltering structure. In still another
feature, at
least a portion of the path is over-spanned by a movable crane, the crane
being operable to
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engage pieces of the sheet material. In a further feature, the path has the
form of a
continuous circuit. In an additional further feature, the path includes
alternate branches
by which more than one carriage can be conducted to a position for interaction
with the
cutting head. In a still further feature, the apparatus has more than one
cutting head
operable to cut profiles in material transported by the carriage.
In yet another feature, the path includes alternate branches, the apparatus
includes
more than one carriage and more than one cutting head, and the carriages can
be directed
to the alternate branches for engagement by more than one cutting head at a
time. In still
another feature, the carriage is a first carriage, and the apparatus includes
at least a second
carriage, and the first carriage is movable to the loading position while the
second
carriage is in the cutting position. In still another feature, the carriage is
a first carriage,
the apparatus includes at least a second carriage, and the path includes an
unloading
position clear of the cutting position.
In a further feature, the first carriage is movable to the unloading position
while
the second carriage is in the cutting position. In still another feature, the
unloading
position is mounted within a sheltering structure. In again another feature,
the first
carriage is movable between the unloading and loading positions while the
first carriage is
in the cutting position. In another feature, the apparatus includes a first
drive train
operable to move the carriage along a first axis relative to the cutting head
in the cutting
position. In another feature, the apparatus includes a second drive train
operable to return
the carriage to the loading position.
In another aspect of the invention there is a process for the manufacture of
rail
road car side sheets including the steps of: placing a steel sheet having a
length at least
half as great as the length of the rail road car on a carriage; passing the
carriage to a
cutting position; and employing a cutting tool to cut a portion of the profile
of the rail
road car in the sheet.
In an additional feature of that aspect of the invention, the step of placing
is
preceded by the step of de-coiling at least a portion of a coil of steel
sheet, and the step of
placing includes placing the sheet so uncoiled on the carriage.
In a further aspect of the invention, there is a plasma arc cutting process
for
cutting steel sheet the process comprising the steps of: placing a sheet of
steel to be cut on
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a movable carriage; moving the carriage to a cutting position; operating a
plasma arc
cutting tool to cut a part profile in the sheet; and moving the carriage away
from the
cutting tool.
In another feature of that aspect of the invention, the step of moving the
carriage away
from the cutting tool is followed by the step of moving another carriage into
the cutting
position, and cutting material placed on that other carriage. In another
feature the step of
moving the carriage away from the cutting position is followed by the step of
unloading
the carriage while another carriage is being cut by the cutting tool. In
anther feature the
step of unloading the carriage occurs while a third carriage is being prepared
for
movement to the cutting position. In still another feature, the process
includes
repetitively moving the camages through a cycle of steps of loading, cutting,
and
unloading. In still another feature, the process includes moving the carriages
along a
circuit, the circuit including at least the cutting position and a loading
position.
In still another aspect of the invention, there is a plasma arc cutting
apparatus
including: a plasma arc cutting head, the head being mounted to move in two
directions
to permits the cutting head to cut profiles in a stationary planar workpiece;
and a movable
bed for supporting a planar workpiece. The movable bed is movable to a cutting
position
in which the cutting head is operable to cut the work piece, and the movable
bed is
operable to transport the workpiece away from the cutting head when cutting of
the
workpiece has ceased.
In another feature of that aspect of the invention, the apparatus includes a
plurality
of movable beds, a first of the movable beds being movable to occupy the
cutting position
after a second of the movable beds has been moved away from the cutting
position. In
still another feature of that aspect of the invention, the movable beds are
constrained to
move in a circuit between the cutting position and a loading position.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a schematic plan view of a factory having a plate cutting
facility
according to the principles of the present invention;
Figure 2 shows a schematic plan view of an alternate of the factory of Figure
1;
Figure 3a shows a smaller version of Figure 1 illustrating a stage in the
cyclic
procedure for cutting metal sheets;
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Figure 3b shows a stage following the stage of Figure 3a;
Figure 3c shows a stage following the stage of Figure 3b;
Figure 3d shows a stage following the stage of Figure 3c;
Figure 3e shows a stage following the stage of Figure 3d, returning to a state
similar
to that of Figure 3a;
Figure 4 shows in perspective view of the plate cutting facility of Figure 1;
Figure 5a shows a partial cross-section of a material transporting carriage of
the plate
cutting facility of Figure 1;
Figure 5b shows upper and lower wear lows as employed in the carriages of
Figure
5a;
Figure 6a shows a chassis layout schematic for secondary carriages of the
plate
cutting facility of Figure 1;
Figure 6b shows a detail of a motor installation of a secondary carriage of
Figure 6a;
Figure 7a shows a view looking along the return portion of a transport path of
the
factory of Figure 1, indicated as '7a' on Figure 1;
Figure 7b shows an oblique view of a transition drive train of the factory of
Figure 1
indicated as '7b' on Figure 1;
Figure 7c shows a detail of a camage pulling and pushing towing head of the
secondary carriage of Figure 6a;
Figure 8a shows a view of an exhaust manifold for the cutting facility of
Figure 1
with one exhaust manifold port open; and
Figure 8b shows a detail of a control assembly for the exhaust manifold of
Figure 8a.
DETAILED DESCRIPTION OF THE INVENTION
The description which follows, and the embodiments described therein, are
provided by way of illustration of an example, or examples of particular
embodiments of
the principles of the present invention. These examples are provided for the
purposes of
explanation, and not of limitation, of those principles and of the invention.
In the
description that follows, like parts are marked throughout the specification
and the
drawings with the same respective reference numerals.
In terms of general orientation and direction nomenclature, reference is made
below to advance and return, and to transverse motion. For the purposes of
this
description the cutting process pertains to cutting a generally horizontally
planar sheet or
plate with a vertically oriented cutting tool. Relative motion between the
cutting tool and
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the sheet or plate is two-dimensional motion that can be described in terms of
components
lying along two axes in a horizontal plane. For the purposes of this
description those axes
will arbitrarily be given the nomenclature of x and y axes, the x, or
longitudinal, axis
lying in the direction of advance or return of the sheet or plate, and the y,
or transverse,
axis lying perpendicular to the x axis.
In Figure 1, a manufacturing facility is indicated generally as 20. It
includes a
sheltering structure in the nature of a factory building or shop 22 that has a
yard 24 having an
accessway, such as a road 23 or rail siding 25 by which raw stock materials
can enter the
plant and finished products may be shipped to market. Shop 22 includes a bay
26 in which a
metal cutting apparatus in the nature of a multi-head plasma-arc cutting
facility 28 is located.
Cutting facility 28 includes a longitudinally movable spanning member, termed
a
burn carriage, or bridge 30 located to straddle a pathway, or track, of a
material transport
apparatus or, transfer system 32, described more fully below. Bridge 30 is
mounted on
wheels 34 at either end, wheels 34 being mounted on a pair of parallel ways
36, 37 to permit
travel in the x direction. Bridge 30 has an electric geared drive 38 that is
operable in co-
operation with toothed racks adjacent to ways 36, 37 to move bridge 30
longitudinally with a
level of precision appropriate for cutting a profile in the work-piece
material. Cutting
facility 28 includes four plasma-arc cutting heads 40, 41, 42 and 43, all
mounted to bridge
30, and each being operable to move along the span (that is, in the y-
direction) of bridge 30
to permit cutting of objects located beneath bridge 30 as required. In
addition to x-y motion
the cutting heads can also be titled to produce a bevelled, or chamfered edge.
Cutting
facility 28 is controlled numerically by a computer 46 mounted beside the
operator console
44 the cutting heads 40 to 43 being employed to cut profiles in sheets of
material according
to design infonnation fed into a computer 46.
Transfer system 32, follows a path, indicated generally as 48, in the form of
a
rectangular continuous loop, or circuit. Path 48 has a first portion 50
running in the
longitudinal, or x direction. Moving frames, or carriages, indicated as items
52, 54, 56, 58,
and 60 are provided to transport sheets of material to be cut in an advancing
direction, as
generally indicated by arrow 'A' (parallel to the x-axis). The camages convey
the sheets or
plates to a cutting range, or cutting zone (namely the burn position indicated
generally by
arrow 'B'), where the sheets are cut according to chosen design profiles input
to computer
46. Transfer system 32 includes a second, or return, portion 64 by which
carriages from the
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output side of cutting facility 28 can bypass cutting heads 40 to 43 and be
retulned back to
the input side of cutting facility 28.
Transfer system 32, in addition to advance portion 50, and return portion 64,
includes a first, or input, lateral transfer portion 66 by which carriages can
be moved on
secondary carriages in the nature of a lateral transfer cart, or shuttle 68,
that is movable along
transverse portion 66 in the transverse, or y direction on a between return
portion 64 and
advance portion 50 on the input side of cutting facility 28. Transfer system
32 also includes
a second, or output, lateral transfer portion 70, also running in the y-
direction, across which
the carriages can be moved on another secondary carriages in the nature of a
second lateral
transfer cart, or shuttle 72, that is movable along transverse portions 70 in
the transverse, or y
direction, between advance portion 50 and return portion 64 on the output side
of cutting
facility 28.
Transfer shuttles 68 and 72 are wider in the x direction than carriages 52,
54, 56, 58,
and 60 are long, and have first and second ways 74, 76 spaced to match the
ways upon
which those carriages travel in advance portion 50 and return portion 64. When
shuttle 68,
or 72, is aligned with advance portion 50, a carriage, such as carriage 52 or
54, can be
advanced from portion 50 and onto ways 74, 76 of shuttle 72. When carriage 52
is thus
positioned, shuttle 72 can be moved transversely (in the +y-direction, until
aligned with the
ways 78 of return portion 64. When aligned, carriage 52 or 54 can be urged
backwards, that
is, in the return or -x direction, out of shuttle 72. In the illustrations of
Figures 1, 2 and 3a to
3e the size of carriages 68 (and 72) is exaggerated relative to carriages 52 -
60 for the
purposes of clarity of conceptual explanation.
In the embodiment illustrated in Figure 1, transfer system 32 includes a
loading zone
(indicated generally by arrow 'C') adjacent to the return portion 64 lying
generally to the
input side of cutting zone 'B'. Similarly transfer system 32 has an unloading
zone, indicated
generally by arrow 'D', adjacent to return portion 64. In the general course
of operation, the
carriages are loaded with new stock at loading zone 'C', moved across input
transfer portion
66 on shuttle 68, and advanced along portion 50 in the direction of arrow 'A'
to a cutting
position in cutting zone 'B'.
When in the cutting position, also called the "burn position", the particular
carriage
is, or carriages are, temporarily locked in position against stops mounted in
a fixed, known
reference position. The first stops 80, 81 have the form of retractable
electrically grounded
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posts having an electrically conductive platen facing whichever of the
carriages is located in
the adjacent buln position. Stops 80, 81 can be lowered when it is desired to
move carriages
with cut materials out of the burn position. At the far end of the carriages,
retractable
clamping members 82 and 83 are raised to bear against the opposite end of the
respective
carriages, (such as 52, 54) and tightened, thus squeezing the carriages
between themselves
and stops 80 and 81 respectively, and fixing them in a known datum location
relative to
bridge 30. Clamping members 80 and 81 also employ electrically conductive, and
electrically grounded platens such that the clamping process also serves to
provide an
electrical path from the carriage through which the plasma arc current can
find ground either
through stops 80, 81 or through clamping members 82, 83 or both. Once the
carriage is, or
carriages are, locked in position, bridge 30 and cutting heads 40 - 43 are
moved co-
operatively in the x and y directions to produce the desired profiles.
After the various items have been cut, the carriages are (or carriage is)
unlocked by
releasing clamping members 82, 83, and lowering stops 80, 81. The carriages
can then
continue along advancing portion 50 and onto output lateral transfer shuttle
72 until in
position to be transferred laterally to return portion 64. Once advanced, or,
alternatively at
the same time as they are being advanced, another carriage (or pair of
carriages) such as
carriages 56 and 58 can be advanced into the burn position for cutting. While
the next set of
plates is being cut, the first carriage is moved to the unloading position in
unloading zone
'D'. Once the cut parts are unloaded, the carriages, bearing only the scrap,
are returned to
loading zone 'C' along return portion 64 where the scrap is removed and new
material
loaded. The various carriages can continue around the circuit in a continuous
loop as long as
there is material to be cut.
For the purposes of loading and unloading, manufacturing facility 20 is
provided
with an inside overhead crane, 86 mounted to run along rails 86, 89 mounted to
building
columns 90 inside shop 22. Crane 86 is moveable to overspan unloading area 'D'
and
adjacent work areas 'E' and 'F'. Alternatively, internal roadways G and H
provide access
by forklift such that materials in the unloading bay can be despatched to
other areas of the
plant. Manufacturing facility 20 is also provided with an external overhead
crane 92 running
in the y direction along rails 94, 95 mounted to pillars 96. Crane 92 is
movable over a range
covering loading area 'C', inventory area 'J' and first transfer shuttle 68.
This arrangement
permits loading of carriages mounted in first transfer shuttle 68 either when
in a position
most closely adjacent to inventory area 'J' or when moved further away, as for
example,
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when aligned with first portion 50 and awaiting advancement in the x-direction
to the burn
position.
This arrangement may tend to permit operation of the cutting heads to continue
while finished pieces are being unloaded and new stock is being loaded,
thereby tending to
improve utilization of the cutting heads. It also permits unloading of
finished pieces from
one carriage to occur while new stock is being loaded on another carriage.
In the embodiment shown in Figure 1, first portion 50 of transfer system 32
includes
first and second parallel branches 100 and 102, such that loaded carriages can
advance along
either branch, as selected, and, advantageously, two camages can be in the
cutting zone at
one time such that cutting heads 40 - 43 can operate on more than one work
piece at a time.
The infeed area, indicated generally as K on the input side of cutting
facility 22 is
sufficiently large to accommodate a pair of waiting carriages side-by-side
while another pair
of carriages is in the cutting zone. In general, it is intended that two
camages be un-loaded
and re-loaded one after the other while two other carriages are in the cutting
zone being cut
side-by-side.
It is not necessary that two carriages be cut at the same time, and it is not
necessary
that carriages always be in all of the cutting, loading, and unloading
stations at the same
time. While the five camage arrangement illustrated in Figure 1 is preferred
for a circuit
having a single track return portion, such as portion 64 the system can be
operated with
fewer carriages, or more, according to the space available. It may be that one
carriage is
loaded with material to be cut into a large number of small pieces, implying a
relatively long
cutting time, while another carriage has only a single large piece, or a few
large pieces. In
that case the double branch arrangement permits the faster cut carriage to be
changed out,
and another carriage put in its place, while the slower carriage remains in
the burn position.
Altelnatively, operations can be carried out with a single carriage, but would
generally be
more effective if at least first and second carriages were used.
It is not necessary that the transfer system include a pair of branches in the
cutting
zone. It could include a single unique path, or more than two paths according
to the number
of cutting heads available. Similarly, there need not be a single, unique
return portion, but
rather, as in Figure 2, a system 110 could be provided having a double track
return portion
112. In the case of the embodiment of Figure 2, it would be advantageous to
use six
carriages 52, 54, 56, 58, 60 and 114, given the ability to unload two
carriages side-by-side.
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It is not necessary that transfer system 32 be formed in a rectangular shape,
with four
separate drives each operable to urge the carriages along one side of the
rectangle. For
example, a triangle or other polygon shape, or an oval with large turn radii
could be used.
However, the rectangular arrangement is preferred since it does not require
additional space
for turn radii, does not require curved track to be laid, and does not require
the carriages to
be tulned during operation. Rather, as described, the rotational orientation
of the carriages in
the horizontal plane remains constant throughout the processing operation.
The sheet material to be cut by the apparatus of Figure 1 or Figure 2 is most
typically
steel sheet or steel plate that is substantially planar. That is, it is
material of some thickness
for which the cutting heads will trace out a profile defined in terms of a two
dimensional plot
defined by relative motion of the cutting heads and the work piece, (or
pieces) along of x and
y axes, where the x axis lies in the direction of advance along the ways of
the first portion of
track system 28, (and, parallel to the line of motion of return portion 64),
and the y axis is the
span direction of the bridge of cutting facility 28 along which cutting heads
40 to 43 run.
The steel sheets, or plates that can be transported on the carriages can be of
significant size, according to the width and length of the carriage. In the
preferred
embodiment the carriage width permits plates up to 11 ft.- 4 in. wide and 64
ft. - 10 in. long
and up to about 2 inches thick to be cut. That is, the carriage size
significantly exceeds a 30
foot or 40 foot length, giving greater versatility in the size of parts that
can be cut. Plates of
this size are generally well beyond a size that might otherwise be manipulated
by hand.
Larger tables can be made to permit the cutting of larger plates. In an
additional, optional
feature, as shown in Figure 1 and Figure 2, a de-coiler 120 is provided
between loading area
'C' and an adjacent rail siding 25. Crane 122 is located in a position to lift
coils from rail
road cars running on siding 25 into de-coiler 120. In operation the output
from de-coiler 120
is fed directly onto a waiting carriage, such as carriage 56 mounted on
shuttle 68. Shuttle 68
is then moved to a position to allow another un-coiled sheet or other material
from stock to
be loaded on an adjacent carriage, such as carriage 58 and transferred to a
position to be
moved to the burn position.
Operation of the Embodiment of Figure 1
The sequence of operation of the cutting and transporting apparatus of Figure
1 is
shown in Figures 3a to 3e. To commence, as shown in Figure 3a, carriages 52
and 54 are in
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the first and second slots in the burn position, respectively. Carriages 54
and 56 are in the
corresponding first and second positions of first shuttle 100, and carriage 60
is in the
unloading position on return portion 64. When the cutting of the pieces is
finished on
carriages 52 and 54, they are advanced onto the output transverse shuttle 72,
and carriages
56 and 58 are advanced into the burn position, as shown in Figure 3b. Cutting
commences
on carriages 56 and 58. Shuttle 72 is moved in the +y direction to align rails
124 with the
rails 126 of return portion 64. Unloading of carriage 60 is either complete,
or being
completed.
As shown in Figure 3c, shuttle 72 is moved further in the y direction to a
position in
which its second slot, or second pair of rails, 128 is aligned with rails 126
of return portion
54. Carriage 60, now unloaded, is moved onto rails 130 the second slot, or
both of shuttle
68, and, once any remaining scrap has been removed (typically, to be
recycled), loading
commences either from stock or from de-coiler 120, with the aid of overhead
gantry crane
92 as may be required. Shuttle 72 can be moved in the +y direction to align
the rails 124 of
its second carriage slot or both 132 with the rails 126 of return portion 64
either before,
during, or after camage 60 has been moved to shuttle 68, although it is
preferreble for both
tasks to be performed simultaneously such that rails 126 of portion 64 are
clear when
carriage 52 lines up with them. In that case there need be little or no delay
in moving
camage 52 from shuttle 72 to rails 126. While unloading commences from camage
52,
cutting continues on carriages 56 and 58.
As shown in Figure 3d, carriage 60 has been moved with shuttle 68 in the -y
direction to align the first set of rails 134 of shuttle 68 with the rails of
return portion 64, and
carriage 52, now unloaded, has been moved in the -x direction into the
awaiting first,
carriage slot, or berth of shuttle 68. Unloading of any remaining scrap is
completed, and
then loading of new material commenced, either from the stock of plates, or
from coils
passed through de-coiler 120. Shuttle 72 has been moved in the +y direction to
align its
second slot, or berth 138, with rails 126 of return portion 64, and carriage
54 is moved in the
-x direction onto rails 126 of portion 64 for unloading. As above, the
alignment of the
second slot can take place before, during, or after movement of carriage 52
onto shuttle 126,
but is preferably complete soon enough to permit carriage 54 to be moved as
soon as rails
126 are no longer occupied by carriage 52. Unloading in zone 'C' commences.
Cutting
continues on carriages 56 and 68.
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In Figure 3e, the situation is similar to that of Figure 3a. Cutting on
carriages 56 and
58 is nearly complete. Shuttle 72 has been moved in the -y direction to
position its slots, or
berths, in a position to await loading of two carriages transporting freshly
cut material,
namely carriages 56 and 58. Shuttle 68 has been moved in the -y direction to
align its rails
with those of branches 70 and 72 of portion 50. As in Figure 3a, a further two
loaded
carriages, namely carriages 60 and 52, are positioned in the slots, or berths,
of shuttle 68,
awaiting their turn to advance to the burn position as soon as the slots of
the burn position
are vacated by carriages 56 and 58. Camage 54 is in the process of being
unloaded.
In the example illustrated, the cut parts, 140, have the profiles of grain
hopper car
side sheets, cut in one piece. In the more general case, as also indicated by
the several items
142 in Figure 3a, this cut profile of parts 145 is intended to represent the
cutting of profiles
of a number of parts, from one large part to several parts of smaller size,
whether being a
batch of parts of one type, or a mixture of parts of different sizes.
Operation of the Embodiment of Figure 2
The embodiment of Figure 2, as noted above, differs from that of Figure 1 in
having
a pair of side by side return portion rails 144 and 146. In this instance
shuttles 68 and 72 do
not have to shuffle between positions for transferring carriages in sequence
either to or from
a single track, such as rails 126 of portion 64. Rather, carriages 68 and 72
move to a single
load/unload position, and both carriages can be, and preferably are loaded and
unloaded at
one time, side-by-side.
That is, while two carriages 52, 54 are in the burn position, another pair of
carriages
60, 114 is moved on shuttle 72 to a position for being transferred in the -x
direction onto the
return rails 144, 146 of double branch return position 148, 72. When this
action is complete,
shuttle will reverse and take up its former waiting position opposite the ends
of rails 150,
152 of the burn position. At the same time the third pair of carriages 56, 58
is being
prepared (i.e., emptied of scrap, re-loaded with new material, and transferred
into an aligned
position) on the other shuttle. These activities could be performed in
sequence, rather than
simultaneously, but simultaneous preparation, loading and unloading may tend
to improve
overall productivity.
The system of Figure 2 retains the capability to load one car at a time in
series (rather
than parallel), or to use only one input or output track, either to transfer
carriages between
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sides of the loop or to reflect different cutting speeds according to the cuts
required per
carriage. However, in general the two carriage, side-by-side mode is
considered
advantageous for higher overall productivity for the embodiment of Figure 2.
The
arrangement of Figure 2 may tend to require greater floor space than that of
Figure 1.
Description of Carriages
In the embodiments of Figures 1 and 2, carriages 52, 54, 56, 58 and 60 (and
114) are
rolling frameworks positioned to support the sheets, or plates, to be cut some
distance above
the floor of the bay. Carriages 52, 54, 56, 58, 60, and 114 are all of the
same construction.
They each have a pair of first and second longitudinally extending left and
right hand side
frames 160 and 162. Each side frame 160, 162 has a pair of back-to-back,
spaced apart
channels 164, 166. The channels are maintained in spaced apart parallel
relationship by
intermittently spaced gusset plates 185, 187. Flanged fore and aft wheels 188,
190 are
mounted between channels 184, 186 in a position in which their motion is
constrained to
follow, that is, is guided by the rails running in the x direction. The gauge,
or track spacing,
of the rails of first portion 50, second portion 64, and the rails of the
carriage berths of
shuttles 68 and 72 are all the same, and the spacing of side frames 160, 162
is such as to
yield the same spacing for wheels 168 and 170. Inclined slag deflector skirt
plates 189 are
mounted on the inboard face of inboard channel 186 to discourage accumulation
of slag on
the rails, and to encourage the slag to collect in the slag pans 300.
Each of the carriages also includes fore and aft, horizontally extending end
frame
members, 172, 174 welded across the ends of longitudinal side frames 160, 162.
End frame
members 172, 174 are formed from sections of channel, and co-operate with side
frames
160, 162 to define the basic rectangular form of the camages. The top flange
of side frames
160, 162 and the top flange of end frames 172, 174 all lie in a common plane.
A series of
mounting brackets 176 are spaced along the upper flange of the inner channel
member of
each of side frames 160 and 162, and a pair of cap angles 178, 180 are bolted
to brackets
176, with one toe extending downward, and the other toe extending inward.
In Figures 5a, 5b, each camage has an array, or matrix, of material support
members
made up of lower wear bar carriers in the nature of lower stringers 182, upper
wear bar
carriers in the nature of upper stringers 184, and wear bars 186. Lower
stringers 182 are
made from plate of a length corresponding to the width between the webs of the
inner
channel members of side frames 160, 162, and a height corresponding to the
depth of the
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inner channel members. The ends, or tips, of each of lower stringers 182 are
cut to a profile
matching the intelnal profile of the inner channel member. Lower stringers 182
are made of
steel and are welded in position in spaced vertical planes along side frames
160, 162.
Upper stringers 184 and lower stringers 182 have corresponding knife joints
188,
190, that is, slots, located such that at each crossing of a lower stringer by
an upper stringer,
a downwardly opening slot of a lower stringer aligns with an upwardly opening
slot of an
upper stringer to permit the upper and lower stringers to slide together
vertically, fonning a
cross-hatched matrix. Upper stringers 184 are not welded in place and can be
lifted out for
replacement as required. Given the pitch of lower stringers 182, the length of
upper stringers
184 is such that each upper stringer spans four gaps, or pitches, between
lower stringers 182,
with the ends notched to overhang. The next adjacent upper stringer is also
notched such
that the two longitudinally adjacent upper stringers overlap the last joint.
The upper
stringers are also made from mild steel, and are electrically conductive. The
upper edge of
each upper stringer 184 is also notched with slots or knife joints 192 for
receiving the
horizontally extending wear bars 186.
Wear bars 186 are made of flat bar of a length spanning the carriage between
cap
angles 178, 180, and of a thickness corresponding to the thickness of the
slots, knife joints
192 in the upper edges of upper stringers 184. Wear bars 186 are made of mild
steel, are
electrically conductive, and are not provided with notches. Cap angles 178,
180 serve to
prevent wear bars 186, upper stringers 184 and lower stringers 182 from being
lifted out
when electro-magnets are used to remove work pieces or scrap from the
carriage. Inclined
baffles 194 are mounted longitudinally between lower stringers 182 to
encourage slag to fall
into slag pans 300, and function to discourage slag from clogging the dampers
286 of the
exhaust system.
Wear bars 186, upper stingers 184 and lower stringers 182 are all electrically
conductive, and provide multiple paths by which the plasma arc current can
reach ground
through the side frames and end frames into the grounded platens of stop 80
(or 81) and
clamp clamping member 82 (or 83).
Each of wear bars 186 is a steel bar made from a 11' - 4" long, 4" x'/4" flat
bar (+/-)
set on edge, each flat bar having a length of about 11' - 8" to span the
corresponding
distance between the webs of the inner channels of end frames 82 and 84. There
are 99 wear
bars 186 spaced along the length of each carriage, that length being about 64'
- 10". This
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array of parallel bars provides a matrix upon which work-pieces to be cut can
be supported.
Wear bars 186 are consumable items. That is, when plasma arc cutting occurs,
the arc may
tend to cut to a depth exceeding the thickness of the materials to be cut, and
may notch the
upper edge of the wear bars at the locations at which the desired profile of
the cut crosses
each wear bar. The wear bars also tend to be come encrusted with slag. When
the wear bars
have been used several times they can be changed out for new, unworn bars.
When the upper
edges of the backing bars have been cut many times in this way, such that they
may no long
provide enough points of support to reliably support the work pieces in the
desired
horizontal plane, they are replaced.
As noted to above, the carriages are constrained to follow the fore-and-aft
rails. To
this end, each end frame of each carriage has a drive force interface member
in the nature of
a towing lug 198 for engagement by a drive hook, as described below.
Description of Shuttles
Shuttles 68 and 72 also have the same construction. Referring particularly to
Figures
6a and 6b, each has a rectangular steel ladder frame having side frames in the
nature of wide
flanged beams 200, 201, intermediate longitudinal beams 202, 203 and lateral
beams
204,205, 206 and 207 that pass through the webs of side frames 200, 201 and
intermediate
beams 202, 203. A running rail 210, is mounted to the top flange of each of
beams 200, 201
and 202, 203, the pairs 200, 202 and 201, 203 each being spaced a suitable
distance to
correspond to the spacing of the pairs of rails of portion 50 or portion 64.
Intermediate
transverse brace members 212 extend between members 200, 201, 202 and 203
between the
locations of lateral beams 204, 205, 206 and 207. A longitudinal chain drive
is mounted
mid-way between beams 200 and 202, 201 and 203. Lateral beams 204, 205, 206
and 207
are each made of a pair of back-to-back channels, spaced apart with gussets.
Diagonal
braces 218 tend to assist in keeping shuttle 68 (or 72) square.
At the ends of each of lateral beams 204, 205, 206 and 207 are flanged wheels
208,
209 mounted between the channels of beams 204, 205, 206 and 207 to roll along
rails 220,
222, 224 and 226 mounted in recessed channels in the floor of bay 26. As
noted, rails 220 to
226 extend in the transverse, or y-direction, and permit the shuttle (68 or
72) to move
between positions aligned with portions 50 and 64. Electric motors 230 and
gear boxes 232
are mounted to one end of each of the foremost and aftmost beams 204 and 207,
and
operation of these motors and gearboxes will tend to urge the shuttle in
either to +y or -y
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direction as may be appropriate according to the stages of the cycle. Stops
are provided at
the ends of rails 220 and 226 to prevent overtravel. An operator's platform,
or cab, 234 is
mounted at the far end of shuttle 68, or 72, from which operation of the
shuttles is controlled.
Lateral beams 204, 205, 206 and 207 are each made of a pair of back-to-back
channel
sections, spaced apart with gussets.
Description of Carriage Drives
Referring to Figures 7a, 7b and 7c, as noted above, each of shuttles 68 and 72
has a
pair of motorized chain drives, 228 operable either with a ram head to push
against the
abutment plate of the towing lug to force the carriage out of the particular
berth of the
shuttle, or a hook operable to engage the endplate of the towing lug 198 so
that each carriage
can be drawn into place on the shuttle as required. In addition, return
portion 64 has a chain
drive 234 that is operable to urge carriages out of the unloading zone toward
the re-loading
zone, and a pair of short chain drives 236 and 238 are used to push camages
from the end of
the push stroke of carriage 68 to the buln position. That is, drives 236 and
238 are used to
push carriages, such as carriages 52 and 54, over the threshold of the doorway
of bay 26, and
the last few feet past the doorway into the burn position. These chain drives
have the same
features and differ only in length or in the type of tow head employed. In
that light,
enumeration of the drive components of one chain drive, 240, are to be taken
as being
representative of all of the chain drives, except as specifically indicated.
Each chain drive 240 includes a guide rail assembly 242, along which a motion
transmission member, such as towing head 244 of shuttle 72, runs. Towing head
244 , (or
such other towing head or pusher may be used), is attached to both ends of a
chain 246, that
is carried over an idler 248 at one end of guide rail assembly 242, and a
driven pinion 250 at
the other. Driven pinion 250 is itself mounted on a stub shaft 252 that is
driven by an
electric motor 254 through a transmission chain 256 and an input gear 258. All
of the
elements of chain drive 240 are mounted to the lateral beams 204 to 207 and
the transverse
braces 212, 214 and 216 of the chassis of shuttle 68 (or 72, as may be).
Towing head 244 is of the type used on shuttle 72. Towing head 244 includes a
pushing member in the mature of a prong 260 whose distal end can be positioned
to bear
against the end plate 196 of towing lug 198 of each of the camages, as when it
is desired to
move one of the carriages from shuttle 72 to rails 126 of portion 64. Towing
head 244 also
has a long hook 245 that is swung into place across the walkway to catch on
the chamfered
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upward lip of end plate 196 of towing lug 198. When attached in this way,
operation of the
chain drive of shuttle 72 in the +x direction will cause towing head 244 for
draw a camage
onto shuttle 72.
The towing head of the chain drive of shuttle 68, does not have the long hook,
but
rather employs short retractable hook 262. When either of the chain drives of
shuttle 68 is
driven in one direction, it will tend to force prong 260 to move in the
positive x direction,
thus urging any camage carried on shuttle 68 in the +x direction into the bum
position.
When towing head 244 is in the pushing mode, hook 262 is in the retracted
position.
However, when it is desired to draw a carriage from the unloading position on
rails 126 of
portion 64 onto carriage 168, as for removal of scrap and re-loading, hook 262
is moved, i.e.,
pivotted, to a deployed position to engage the eyelet of towing lug 198, by
which the
particular carriage can be towed. Prong 260 has a sufficient reach to push the
carriage to the
point at which it can be moved with one or other of chain drives 236 or 238
past the door
threshold, and into the burn position.
Chain drives 234, 236 and 238 employ pushers 249 in place of towing head 244.
Pusher 249 is biased by a spring to a raised position. In the raised position
the head of
pusher 249 bears against the end frame of the carriage, whichever it may be,
and, when
driven, urges the carriage along whichever set of rails it is running on.
However, when it is
desried to return pusher 249 to its start position, or when it is desired to
allow a carriage to
pass over pusher 249, the spring allows pusher 249 to deflect pivotally, such
that the head of
pusher 249 moves downward, and forward in the direction of advance of the
particular chain
drive. Once the object has passed overhead, pusher 249 resumes its raised
position. In
summary, the operation of chain drives 228 mounted to shuttles 68 or 72, or
chain drives
234, 236 or 238, in the x direction, and the movement of shuttles 68 and 72 in
the y direction
permits the various carriages to be urged around the circuit of path 48
between loading (or
re-loading), cutting, and unloading positions.
When a carriage is being loaded into the burn position, clamping member 82 (or
83)
lies in a retracted, or 'down' position shy of the profile of rails 280 of
portion 50, such that it
is clear of whichever of the carriages may next pass overhead. When the
carriage is in
position against stop 80 (or 81) as the case may be, clamping member 82 (or
83) is pivotted
about a longitudinal axis to an upright position. Once in the upright
position, the electrically
conductive platen of clamping member 82 (or 83) is tightened against the end
frame of the
camage, as described above, and cutting can commence. When cutting is
complete,
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clamping member 82 (or 83) is released, and pivoted back to a the lowered
position to clear
the pathway for the next carriage.
Description of Venting System
When the plasma arc cutting heads are in operation, a quantity of noxious
gases and
fumes is produced. The raising of the work piece plates clear of the floor on
top of the
carriages, which are carried on rails 280, mounted on support beams 281,
permits the
installation of a ventilating, or gas extraction apparatus in the nature of a
vacuum system 156
whose intakes draw from the region below the plates under the location of the
cutting heads.
The gases and suspended particles so removed may then be filtered and treated
as may be
required at an external settling device, such as a cyclone or scrubber.
In Winter operation, the vertically moving end doors 277 of the bay are raised
only
far enough to admit entry or exit of the carriages, each of the end doors
being provided with
movable skirt sheets 279, of either rubber or plastic, that hang across the
opening, and are
deflected by the movement of the carriages. The skirt sheets fall back into
place when the
carriages are clear. Fresh air is supplied to the bay by the ventilating fans
of the building
generally (not shown).
Referring to Figures 1, 8a and 8b, the venting system includes an external
dust
cyclone assembly, indicated as 270, mounted outside of doors 272, out of the
way of
movement of shuttle 68. Dust cyclone assembly 270 can include particle
filtering elements,
a liquid scrubbing element, whether of the water curtain of water bath type,
or an
electrostatic type of scrubber, as may be found suitable for the operating
conditions of the
plant more generally. In any case dust cyclone assembly 270 includes a cyclone
for settling
out solid particles, and a blower operable to draw air, noxious gases, and
fumes through the
venting system generally. In the preferred embodiment the venting system
includes three
cyclones and three blowers operating in parallel, although a greater or lesser
number can be
used depending on system design point - that is, at the combination of a
desired volumetric
flow rate, and the corresponding pressure drop through the system at the
desired flowrate.
Dust cyclone assembly 270 is fed by through a common feed duct 274 drawing
from
a pair of first and second inflow manifolds 276 and 278. Feed duct 274 is
routed to pass
below rails 280 of portion 50. Rails 280 of portion 50 are raised on
longitudinal beams to
match the height of the rails of shuttles 68 and 72. This height also gives a
clearance space
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in which to run ducting or to place boxes for the collection of slag. Inflow
manifolds 276
and 278 each have the form of a rectangular duct, or trunk 282, extending in
the x-direction
midway between each of the respective pairs of rails of the first and second
berths, or slots,
of the cutting position 'B'. That is, when carriages, such as carriages 52 and
54 are in the
burn position, and cutting is underway, inflow manifolds 278 lies under
carriage 52, and
inflow manifold 524 lies beneath carriage 54.
In each case trunk 282 has a series of ports 284 formed in its upper wall,
each of the
ports having a closure member or door, or damper, 286 movable between an open
position in
which gases can flow into trunk 282, and a closed position in which flow is
impeded. Each
of dampers 286 is controlled by a pneumatic actuator 288. Each of actuators
288 is operable
in response to a pneumatic signal carried from a pneumatic switch valve 290
mounted
adjacent to the running rails of burn carriage, namely bridge 30. Each
pneumatic switch
valve is actuated by pressing downwardly on an upwardly biased valve actuator,
in the
nature of a spring loaded cam follower. The cam follower in this instance is a
roller 292.
The pneumatic switch valves of manifold 278 are aligned in a first row
extending in the
longitudinal, x, direction, and the pneumatic switch valves of inflow manifold
276 are
aligned in a second longitudinal row, offset from the row of the switch valves
of inflow
manifold 278.
The burn carriage 30 has a shoe 294 mounted at one end thereof. Shoe 294 is
operable to control the position of valves 290 as burn carriage 30 travels in
the x direction.
Shoe 294 has two downwardly facing cams, one for the switching valves of
inflow manifold
278, and the other for the inflow valves of manifold 278. Shoe 294 can be
raised
pneumatically to run completely clear of switch valves 290, such as where burn
carriage 30
is running to a disengaged position without any of the plasma arc cutting
heads in operation.
The cams of shoe 294 can also be lowered so that it operates each one of
switching valves
290 as they are encountered in tuln. In a further alternative, where cutting
is occurring on
only one carriage, shoe 294 can be positioned to engage the switching valves
290 of only
one of inflow manifold 278 or inflow manifold 278, so that cases are drawn
only from under
the camage subject to cutting.
As the butn carriage moves, the cams engage the cam followers, causing the
dampers of the ports most closely adjacent to the cutting operation to open,
and to remain
open while cutting is in that vicinity. When the cutting heads move away,
those dampers
close, and the next adjacent dampers open. In this way, the opening in the
manifold moves,
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in effect, to follow the cutting heads as the burn carriage moves
longitudinally. At any time
at least one damper 286 is open, and in transition, two dampers are relatively
briefly open
together. As a result, venting system provides a sink, or low pressure area,
adjacent to the
cutting heads toward which gases and fumes tend to be drawn. Inasmuch as the
matrix of
lower strings 182, upper stringers 184 and wear bars 186 provides a plurality
of vertical
pathways for gas to be drawn downwardly, and given that the work-piece
material tends to
form a barrier to passage of the air downwards, the area under the matrix of
stringers will
itself tend to act as a plenum, the gas and fumes most close to the open port
of the inflow
manifold will tend to be most strongly urged toward the manifold, when they
can be
exhausted from the bay.
To either side of either inflow manifold 276 or 278, between the vertical side
walls
of trunk 282, and the adjacent rails 280 there is a space into which, in the
general course of
cutting, undesirable materials may tend to collect, such a blanks cut from the
work pieces,
slag, soot, and so on. To facilitate removal of this unwanted material, slag
boxes, or slag
pans 300 are placed in close fitting positions between trunk 282 and each of
the rails to
either side. Each slag box has four upright sides assembled to form the
peripheral walls of a
rectangular box, and a base, forming the bottom of the box. Each box also has
a pair of
lateral internal partitions, typically dividing the box in three roughly equal
portions. The
partitions are provided with lifting holes, such that when the boxes approach
full, they can be
lifted out by crane and replaced.
Various embodiments of the invention have now been described in detail. Since
changes in and or additions to the above-described embodiments may be made
without
departing from the nature, spirit or scope of the invention, the invention is
not to be limited
to those specific embodiments.
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