Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: SYSTEM AND METHOD FOR MANUFACTURING
WINDOW FRAMES
FIELD OF THE INVENTION
This invention pertains to the manufacturing of vinyl or aluminum window
frames, and more particularly, it pertains to the tracking of every frame
element during the manufacturing of window frames, and the generation of
machine and operator instructions for each frame element.
BACKGROUND OF THE INVENTION
The manufacturing of window frames is a complex process. Broadly
described, this process includes two parts. The first part comprises the
cutting, machining and welding frame elements to form rectangular
window frames. The second part includes the assembly of hinges, seals,
locks, thermos panes, bug screens, and packaging for shipping.
The first part of the process, including the assembly of window frames,
includes the most difficult operations in the manufacturing of vinyl and
aluminum windows. This portion of the process is carried out in the frame
machining and welding room. Long extrusions are handled over machinery
and in tight spaces. These extrusions are set in jigs and are carefully
aligned
with the bed of each machine. Precise cutting, machining and welding are
critical as dimension tolerances are very small. Verification of work
quality requires frequent measurements and an extensive knowledge of all
the extrusion profiles at hand. These operations require skills and
concentration at all times to avoid errors.
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In the past, several systems were developed to facilitate the machining of
extrusions that are used in the window manufacturing industry. Some
examples of the systems found in the prior art are:
US Patent 5,022,143 issued to J.J. Kautt on June 11, 1991;
US Patent 6,294,044 issued to M. Schwaiger on Sept. 25, 2001;
US Patent 6,860,181 issued to P. Aubourg et al., on Mar.1, 2005.
The first-mentioned document pertains to the assembly of hardware to a
window frame. The second document pertains to the joining of frame
elements, and the third document pertains to the collating of kits in the
manufacturing of aluminium window frames. The collating of the frame
elements is done after the cutting and machining of the frame elements.
It is believe that the most important improvements in the manufacturing of
vinyl windows can be accomplished during the first part of the process as
mentioned before, that is in the frame machining and assembly room. It has
been found that most of the idle time and rejects are generated during the
cutting of extrusions and the machining and welding of these extrusions
into rectangular frames. After analysis of a typical window manufacturing
plant, it has been found that the predominant areas of improvement in the
plant were:
a) Idle time when searching for material;
b) Defects occurring during welding;
c) Dependence on employee absenteeism.
Idle Time: In a typical window manufacturing plant, a single worker can
walk over a distance of 5,200 feet during the production of a single window
box. These displacements include primarily the searching of frame
elements and the transport of frame elements from inventory to and
between work stations. As a consequence, a limited production of 10-12
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window boxes per employee per 8-hr.-shift has been considered in the past
as an acceptable daily production.
Defects Generated During Welding: Although walking time in a
manufacturing plant contributes greatly to overall waste, the welding of
vinyl extrusions is known the generate numerous defects. Twin head
welding machines for example, have different heat characteristics and
different melt factors on different extrusion sizes. Both heads in a welding
machine may also have different heat characteristics and different melt
factors.
When a window frame is welded without taking the melt factors in
consideration, the joints on that window frame may not be perfectly square.
The amount of material that is melted in a joint is not consistent from one
size of extrusion to the next, or from one side of the window frame to the
other. As a consequence, the window frame does not have square joints.
The opening panel will not fit in that frame, the thermos pane will not fit,
and the bug screen will not fit. The brick molding will not fit around that
frame either. Therefore, a window frame that is not symmetrical and
square must be rejected as waste.
Twin head welding machines are the most popular equipment in the vinyl
window frame manufacturing industry and therefore, manufacturers
continue to have considerable amount of rejects due to improper welding.
Employee Absenteeism: Employee absenteeism is always a problem for
manufacturers, and especially when several work stations depend on each
other for a constant supply of workpieces through the plant. During the
assembly of window frames for example, the machining of hardware-
mounting slots and drain holes must be done before the frame elements are
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welded together, and the machining cannot start before these frame
elements are cut to length. Therefore, the machining center is dependent on
the output of the cut-off saw, and the welding machines are dependent on
the flow of workpieces through machining center.
In view of these main areas of study, it is believed that there is a need for
improvement in the cutting, machining and welding of vinyl window
frames. There is still a need in this industry to reduce rejects and to
improve productivity and quality.
SUMMARY OF THE INVENTION
In the manufacturing system and method according to the present invention
for manufacturing window frames, there is provided a computer system and
an array of boxes that are closely associated with addresses in a database
of the computer system. This computer-box association is used to keep
track of the sequence, placement and presentation of each window frame
element to each workstation. This association is maintained until these
frame elements are assembled into rectangular window frames. Then,
individual window frames are tracked into other workstations using bar
code labels.
In a first aspect of the present invention, there is provided a method for
manufacturing window frames. As mentioned above, a cart with an array
of boxes is associated with an array of addresses in a database of a
computer. An order for window boxes is received and read by the
computer. Dimensions of extrusions are extracted from this order. Machine
and operators instructions are generated for cutting, machining and
welding frame elements for making window frames for the order.
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The operator and machine instructions are downloaded to a cut-off saw.
The operator of the cut-off saw is instructed to cut frame elements from
stock extrusions, and to place individual frame elements in a specific one
of the boxes. When the cart is full of frame elements, it is moved to a
machining center. Operator and machine instructions are downloaded to
the machining center. Instructions to the operator of the machining center
includes instructions to orderly handle each frame element from the boxes
to the machining center and from the machining center back to its
respective box.
When all frame elements in a cart have been machined, the cart is moved
to a welding station. Operator and machine instructions are downloaded to
a welding station. Instructions to the operator of the welding machine
includes instructions to orderly handle the frame elements from the boxes
and into a specific head of the welding machine.
During the entire process taking place in the machining and welding room,
operator and machine instructions are individualized for each frame
element such as to make it easier to the operators and such as to avoid
mistakes and defects.
In another aspect of the present invention, there is provided a system for
manufacturing window frame. This system includes a computer; several
workstations and a cart for transporting window frame elements between
the workstations. The cart has an array of boxes therein, each of these
boxes has dimensions for receiving one window frame elements therein.
The cart is movable between workstations. The computer has a database
and this database includes an association of each of the window frame
elements with a respective one of the boxes; operator instructions for
handling each of the window frame elements in and out of the boxes at
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each workstations; machine instructions for machining each window frame
elements; and welding instructions for welding each window frame
elements to form window frames. In this system, operator instructions are
reduced to the manipulation of frame elements on and off the different
machines, basically.
In yet another aspect of the present invention, orders for window frames are
grouped into batches of frame elements. These batches are accumulated as
work banks before each workstations. Workstations are computer
controlled, and instructions to operators are very elaborate. Workstations
can operate independently of the other workstations or with reassigned
operators for an extended period of time, which make these workstation
less dependent on absenteeism in the plant.
In a further aspect of the present invention, there is provided a method for
welding a vinyl window frame on a twin-head welding machine. This
method includes the steps of:
- determining the melt factor of each head in the welding machine;
- determining a placement of individual end of each frame element in a
window frame in a respective head in the welding machine;
- adjusting a length of each of these individual end of each frame element
for compensating for the melt-factor of that respective head,
- placing the individual end of the frame element in the respective head of
the welding machine and welding that end to another end of another
frame element, forming a joint in the window frame.
As a result, the time required for machining and assembling each window
frame is significantly reduced. Defects from welding is also significantly
lower. For example, the material searching time and employee walking
time has been mostly affected. Whereas a worker used to walk over a
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distance of 5,200 feet per window box, this distance has been reduced to
less than 300 feet per window box per employee. Average production has
been doubled, to 25 window boxes per employee per 8 hr. shift.
As it may be appreciated, such an improvement in efficiency has been
accompanied by a reduction in human errors, and an improvement in
employee satisfaction.
This brief summary has been provided so that the nature of the invention
may be understood quickly. A more complete understanding of the
invention can be obtained by reference to the following detailed description
of the preferred embodiment thereof in connection with the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention is illustrated in the
accompanying drawings; in which:
FIG. 1 is an elevation view of a typical window frame;
FIG. 2 is a schematic plan view of the frame machining and welding room;
FIG. 3 is a schematic elevation view of a conveyor system for carrying
frame elements throughout the frame machining and welding room, as seen
along line 3-3 in FIG. 2;
FIG. 4 is a logic diagram explaining the computer program that is used to
control manufacturing equipment in the window frame machining and
welding room.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, a typical window frame is illustrated therein for
reference. For the purpose of keeping track of the elements in a window
frame, label "A" is assigned to the window sill; labels "B" and "C" are
assigned to the left and right side members respectively; and label "D" is
assigned to the header of the window frame. This labelling is used by the
computer system and by the plant personnel to keep track of the location
of each frame element during manufacturing. This labeling is also used to
assign machining instructions required to work each frame element.
Referring now to FIGS. 2, 3 and 4 simultaneously, the preferred system
and method according to a preferred embodiment of the present invention
will be described.
Orders are received and logged in a computer system. This computer
system is managing the companies' accounting, sales records and
production. The logic diagram in FIG. 4 explains the different steps
involved in the software that is used in the preferred method and system.
The portion of this computer system that is of interest herein is the portion
that pertains to production. That portion starts at step 100 in FIG. 4A.
More particularly, the portion that is of interest herein is the cutting and
machining of frame elements and the welding of these frame elements into
a rectangular window frames as shown in FIG. 1 for example. The
remaining steps in the process for manufacturing window boxes include
other innovations that may be best described in other documents. These
remaining steps are not the focus of the present invention, and therefore,
they are not explained in great details herein.
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The logic diagram that is illustrated in FIGS. 4A-4D, explains steps that
are carried out inside the computer processor and steps that are carried out
on the production floor by operators and by machines. The diagram has
been prepared this way to facilitate the understanding of the preferred
manufacturing system.
Orders for window boxes are received and sorted by expected delivery
dates. Orders are analyzed at step101 to determine the stock material that
is required, and whether or not the material is available. When stock
material needs to be ordered, this is done at that time. However, a good
inventory of all standard frame elements is preferably kept at the plant at
all times.
Each order is analysed by the computer system and a database is generated.
Each order is separated into types of extrusions, at step 102. The computer
system forms convenient-size batches of"N" window frames to be handled
in the frame machining and welding room. Two or more orders may be
grouped together to form a convenient-size batch, in step 103.
A typical convenient-size batch of "N" window frames would comprise 45
window frames for example. The convenient-size batch "N" is determined
by taking into account machine set-up time, jig set-up time, and storage
space for the work in progress. In the database, similar frame elements are
grouped together into production "runs", in step 104.
The computer keeps track of the location of each frame element throughout
the machining and welding room. The method and system used to keep
track of each frame element in the machining and welding room will be
understood from the following description of the different machines and
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workstations included in the machining and welding room.
Main Fabrication Line
At a first workstation, as illustrated in FIG. 2, the stock extrusions 20 are
cut to length in a computer-controlled cut-off saw 22. Full-length stock
extrusions 20 are stored in several overhead trolley wagons 24, 26, 28 that
are hung to rails 30 above the bed of the cut-off saw 22. The overhead
trolley wagons 24, 26, 28 are large enough to contain extrusion profiles 20
for several days of full plant production. The overhead trolley wagons24,
26, 28 are mounted next to an access door 32 in the building so that these
trolley wagons can be re-loaded easily with full-length extrusions using a
forklift truck for example moving through that door 32.
The computer file that is downloaded to the cut-off saw 22 requires an
operator 34 to cut all the extrusion types in a production "run" from a first
trolley wagon 28 for example, before moving that first trolley wagon 28
aside and cutting a second type of extrusions from a second production
"run" from the next trolley wagon 26 and then 24 and so on. When
extrusions from all trolley wagons have been cut, the computer file that is
downloaded for the next batch will ask the operator 34 to cut the extrusions
in the reverse order; that is from the trolley wagons 24, 26, and 28, such as
to improve efficiency. Preferably, a total of five trolley wagons are used for
providing a combined total storage space for two weeks of production.
The computer file or database that is downloaded to the cut-off saw 22
includes machine instructions to cut each extrusion along the proper angle
and at the proper length, and instructions to the operator 34 of the cut-off
saw to place each cut frame element in a specific orientation into a specific
box 40 in a storage cart 42.
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As it may be understood, the computer file that is downloaded to the cut-off
saw 22contains a grouping of similar lengths of a same extrusion type.
These sub-grouping within each batches of "N" window frames constitute
the aforesaid production "runs".
Therefore, it is common to cut from a work batch of 45 window frames for
example, a side member for window frame # 5 in the batch, and then cut a
side member for window frame # 23, and then another frame member for
window frame # 33, and so on, until all similar extrusions have been cut.
The cutting appears to be done randomly, but at the end of the batch, all
frame members for the batch of window frames are accounted for in the
carts 42.
Several storage carts 42 are mounted on rails 44 and are driven along the
rails by conveyor chains (not shown). These carts 42 are moved along the
rails 44 and are parked at each workstation. In the preferred embodiment,
each cart contains fifteen columns each containing four boxes 40 stacked
on top of each other. A parking sign 46 at the cut-off saw 22 shows the
numbers from 1 to 45. In use, three carts 42 are moved to this workstation
22 and the columns are aligned with the numbers on the parking sign 46.
As mentioned, the computer file or database that is downloaded to the cut-
off saw 22 includes instructions to the cut-off saw 22 to cut each extrusion
at the proper angle and length. This computer file tells the operator 34 of
the cut-off saw 22 to place each cut extrusion in a specific orientation into
a specific box 40 in one of the three storage carts 42. One example of a
proper placement of the frame element 20 in each box 40 is: a window sill
member "A" is to be placed in the lower box; the left side extrusion "B"
goes into the second box 40; the right side extrusion "C" goes into the third
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box 40 and the header goes into the fourth or the top box 40. Each column
of boxes 40 contains the extrusions required to fabricate one window
frame.
The instructions to the operator 34 of the cut-off saw also include an
instruction to place the extrusions with their exterior surface facing right
or
left inside its respective box 40. The placement of each extrusion in each
box 40 facilitates the handling of these extrusions by the operators of
downstream workstations. A right side frame element would have its
outside surface facing to the right, and a left side frame element would have
its outside surface facing to the left for example.
A bar code label is made available at the bar code printer 48. The bar code
printer is mounted above the cut-off saw 22. The bar code label is affixed
to the outside surface of each frame element by the operator 34 of the cut-
off saw, before these frame elements are placed in their respective box 40.
When a first batch of "N" window frames has been completed at the cut-off
saw 22, a train of three carts 42 is moved along the rails 44 to the second
workstation; that is the machining center 50. The computer file that is
downloaded to the machining cente50 contains instructions to the operator
36 regarding the sequence and location of each piece to be taken from a
cart 42; the placement of that piece on the machine 50, and instructions to
the machine 50 to cut slots and to drill holes where required on that piece.
The operator 36 is also instructed to place the finished extrusion exactly the
same way as it was taken from its respective box 40.
When the machining of all the extrusions 20 in one cart 42 has been
completed at the machining center 50, that cart 42 is moved upward by a
first elevator 52 onto a second level of the previously-mentioned conveyor.
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Carts 42 on this upper level are moved along rails 44' to the welding station
60.
The preferred welding station 60 comprises three welding machines 62, 64,
66. Each welding machine in the preferred installation is a twin head type
machine, although four head machines can also be used. Each machine is
set up with jigs for specific extrusion profiles. The designation of these
welding machines to perform welds on specific window frames will be
better understood later when describing the welding machine operations.
In order to further facilitate the operator's task at the welding workstation
60, each cart 42 preferably has transverse slides 66 there under and each
cart 42 can be moved perpendicularly from the rails 44' to be brought
closer to the welding machines 62, 64. This provision also saves work and
production time. The display screen at the welding station instructs the
operator 38 to place each frame element in the welding machine that has
been selected for that extrusion type. The instructions to that operator 38
also includes instructions to place each extrusion under the welding head
for which the length of that extrusion has been adjusted, as it will be
explained later.
After a cart 42 has been emptied at the welding station 60, the empty cart
42 is returned back inline with the rails 44' and moved toward the cut-off
saw 22 on the upper deck of the conveyor. A second elevator 52' brings
the cart 42 back to the lower level to be used again at the cut-off saw
workstation 22.
The welds on each window frame are cleaned in a weld-cleaning machine
70. Then, each window frame is stacked vertically in a side-by-side order
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on a first transfer dolly 72. The first transfer dolly 72 is movable on
another
conveyor 74. This other conveyor 74 carries the window frames to other
workstations in the manufacturing plant. Tracking off each window frame
in the plant is done thereafter using bar code readers at the other
workstations.
For information purposes, the additional workstations that are required to
manufacture complete window boxes include: Hardware Installation;
Thermos Installation; Brick Molding Installation; Bug Screen Fabrication
and Installation; and Thermos Inspection and Sorting. The bar code label
that is affixed to each window frame at the cut-off saw 22 is also used to
track the location of each window frame in the plant's shipping warehouse.
Because the cut-off saw 22 and the machining center 50 are computer-
controlled, and because of the exact placement of all the extrusions in
respective boxes 40, a same operator can operate both machines. That
same operator can also operate all three welding machines. Because of the
grouping of identical extrusion profiles within a same batch of window
frames in a production run, changes of jigs and fixtures at every machine
are minimized. As a result, this manufacturing system is more efficient
than all known prior art systems.
Brick Molding Line
The machining and welding room includes a parallel line that is used to
fabricate brick moldings when required in an order. The extrusions
required to make these brick moldings are cut to length on the cut-off saw
22 and are placed in the transfer carts 42. If machining is required, they are
transported in one of the carts 42 to the machining center 50. The cut
extrusions are then welded on the welding machine 66. This welding
machine 66 is equipped with a jig that is made for brick molding extrusion,
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and that jig is left on that machine as much as possible. In other words, this
welding machine 66 is dedicated to do joints on brick moldings frames
only.
The welds are cleaned on the weld cleaner 70, and the assembled and
cleaned brick molding frames are placed on a second transfer dolly 80 for
transport directly to the brick molding mounting station. In the preferred
installation, the second transfer dolly 80 is mounted to an elevator 82 for
movement through an opening 84 in the floor of the machining and welding
room. From there, it is conveyed to the brick molding mounting station.
Bypass Line
Referring to FIG. 3, a by-pass line 90 comprises a bypass cart 92 that is
similar to but with less compartments 40 than the previously mentioned
carts 42. The cart 92 is hung to rails 94 that are attached to the ceiling of
the machining and assembly room. The cart 92 follows the same path as
carts 42 between the cut-off saw 22, the machining center 50 and the
welding station 60. This by-pass line 90 is used to manufacture small
orders and replacement frames that may be required from time to time at
a downstream station, to replace a defective frame in an ongoing order, for
example.
Twin Head Welding Machines
As mentioned before, twin head welding machines have a specific melt
factor for each extrusion profile. These melt factors must be known and
understood to ensure consistent work quality. All three welding machines
62, 64, 66 have been tested with different extrusion sizes. Their welding
heads have been tested independently. The characteristics of these
machines have been noted.
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Referring back to FIG. 4A to 4D, the preferred computer system
controlling the fabrication process will be explained. At step 105 and 106,
the computer determines from the aforesaid production "runs", the type of
extrusion that has been selected for each frame element. These frame
elements are grouped in three types. The first type is a larger extrusion that
is used for the outside frame of a window box. The second type is a
smaller extrusion that is used for the framing of the movable panels inside
a window frame. The third type is a smallest extrusion that is used as a
brick molding as mentioned before. A determination is made to assign the
welding of each extrusion to a specific head in a specific welding machine.
In steps 107 to 110, the computer uses a sub-routine to defines the
dimensions of the frame elements and to adjust the cutting instructions to
leave the exact amount of material that is required to weld all four joints in
the window frame. The computer also adjusts the machining instructions
to compensate for the added material and adjusts the weld time,
temperature and jig displacement of the selected welding machine for
performing an ideal weld on each joint in each window frame.
While the cutting instructions to the cut off saw 22 may contains a single
total length adjustment to compensate for the weld factors of both joints in
a same extrusion, the instructions to the machining center take into
consideration individual melt-factor for each end of each extrusion. The
machining of slots and holes in each frame element remains true relative
to a mid-point along each frame element.
Then the computer programs resumes its regular flow in steps 111 and 112.
These instructions are stored in the computer's memory for timely
download to workstations as machine and operator instructions.
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Operator and machine instructions are downloaded to the cut-off saw 22 in
step 113. At that time, the instructions to the bar code printer 48 and the
corresponding feedback are registered in a database in steps 114 and 115.
In step 116 the operator 34 at the cut-off saw 22 receives instructions to cut
frame elements to fulfill the entire batch of "N" window frames. Once the
batch is completed, the bank of frame elements is moved to the machining
center 50 in step 117. Machine and operator instructions are downloaded
to the machining center in step 118, and again frame elements for a bank
of "N" window frames are accumulated in the transfer carts 42, in step 119,
for transfer to the welding station 60.
In steps 120-121, operator and machine instructions are downloaded to the
respective welding machines 62, 64, 66 for joining the frame elements and
making window frames. Each frame element is assigned a specific head in
a specific welding machine, such that the weld melt factor is known and is
as planned.
The joints are cleaned in step 122 and the window frames are loaded onto
the first and second transfer dollies 72 and 80, in step 123, for transport to
other workstations.
Absenteeism
In the present manufacturing system, it is possible to achieve a normal
production with less than full staff. The operator's instructions are
downloaded to each workstation on a display screen so that minimum
training is required to operate the workstations. Every step of every
operation to be done to every frame element is displayed and explained.
The operators' tasks at every workstation are reduced to the manipulation
of the extrusions on and off the machines basically. When an operator has
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learned the sequence of operation of each workstation, that operator can
operate each workstation.
Because of the accumulation of frame elements in batches of "N" window
frames between the cut-off saw and the machining center and between the
machining center and the welding station, the cut-off saw and the
machining center can stay without an operator for a period of time without
interrupting the work flow to and from the welding station.
This process may be better explained by looking at FIG. 4C. During step
116, the computer program keeps count of production and the batch size
"N". When the bank is full, as in steps 140,142, the computer directs the
operator 34 of the cut-off saw to be reassigned to the machining center 50
to help production at the machining center. Similarly, when the bank is full
at the machining center as explained by steps 144, 146, the operator is
reassigned to the welding station 60 to help at that location.
When the bank of "N" window frames has been reached on the transfer
dollies, at steps 148, 150, the operator is reassigned somewhere else in the
plant to help at a downstream workstation, or is reassigned to the cut-off
saw 22.
The batch size of "N" window frames can be adjusted from one day to the
next according to the absenteeism in the plant, according to equipment
maintenance schedule, inventory size, urgency of orders, and other similar
variables. Under the present manufacturing system, operators are more
flexible to work at several workstations. For example three operators can
manage the four workstations in the machining and assembly room, ifthere
is a need for it. Bank sizes for two days of production can be made.
Absenteeism is no longer an impediment to a steady production. The
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overall productivity of the plant is greatly improved.
As to other details of fabrication and operation of the present cover, the
same should be apparent from the above description and accompanying
drawings, and therefore, no further description is deemed necessary.
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