Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR PRODUCTION OF TUBING
BACKGROUND OF THE INVENTION
The present invention relates generally to production of
thermoplastic tubing and formable plastic products and, more
particularly, relates to a method and apparatus for producing
small and large diameter thermoplastic tubing and composite
tubing structures.
DESCRIPTION OF RELATED ART
One known method for manufacturing corrugated pipes is to
extrude a tube of thermoplastic from a head and then conform that
tube to the interior of a corrugated mold tunnel formed by mold
blocks. Mold blocks typically come in pairs and mate together to
form a portion of the mold tunnel, and the thermoplastic is
either blown into shape (by pressure created within the plastic
tunnel) or vacuumed into shape (where vacuum draws the air from
around the mold tunnel). Typically, the mold blocks operate in a
clam shell-type fashion such that each of the mold block pairs
pivot on an axis into mating engagement with one another.
Examples of clam shell type corrugators are shown in U.S. Pat.
Nos. 5,645,871; 5,494,430; 4,439,130 and others. The clam shell-
type shape of mold blocks are susceptible to "sawtooth"
imperfections which can occur throughout the mold tunnel.
Sawtoothing occurs when successive mold blocks are tilted
slightly rather than perfectly aligned with the axis of the mold
tunnel. The hinged mold carrier, when closed, has a tendency to
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lean back in the opposite direction of travel during the molding
process. This "sawtoothing" creates molding lines as well as a
potential loss of vacuum.
The clam shell type mold carriers typically require the use
of multiple custom-machined components and have a high
manufacturing cost. The hinge pin is subject to external forces
which results in wear on the hinge pin. A worn hinge pin may not
allow the mold to pivot closed properly which could prevent the
tubing from forming properly. Furthermore, wear and misalignment
of the pivoting pairs may result in the hinged mold carrier
bending or breaking some of the custom-machined components.
At least one prior art device, U.S. Pat. No. 5,510,071
teaches a pair of mold blocks that are operated differently from
the clam shell variety. Instead of using a hinged pivot, as is
customary in the art, this device allows for transverse linear
reciprocal travel for closing and opening of the mold block pair.
The apparatus taught by the '071 Patent utilizes reciprocal
linear travel for the carriage supporting the mold blocks. There
is no teaching in the '071 Patent to utilize linearly opening and
closing of mold block pairs in a continuous loop corrugator.
Typically mold blocks must be maintained within an
acceptable range of temperatures during the molding process.
However, during the extrusion process, hot plastic is extruded
into the mold blocks which tends to heat the blocks. To maintain
acceptable temperatures the blocks must be cooled. Cooling of
mold blocks may be a problem. Inadequate cooling of mold blocks
may lead to excessive temperatures for the molding process and
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result in degradation of the quality of molded tubes. Too much
cooling may result in crackling of the exterior surface of molded
tubes thereby giving the impression of an alligator-like skin on
the pipe surface. Traditionally, mold blocks have been water
cooled with internal cooling passages within each block. Failure
of water lines and water leakage is a problem for many corrugator
designs. If significant water leaks into the mold cavity during
molding, a defective product may result, requiring the corrugator
to be shut down, the leak located and the mold block or other
leaking component repaired. Accordingly improved cooling
techniques are desired.
In order to keep mold blocks in contact with the product to
produce good forming characteristics, prior art corrugators
utilize chain driven mold blocks where mold blocks are located
substantially around the entire perimeter of a continuous path.
At least one improvement is illustrated by U.S. Pat. No.
5,494,430 and 5,531,583 where a mold train drive and a shuttle
drive are utilized to minimize the number of mold blocks.
Nevertheless, this system relies on gearing and at least two
separate chain drives: one to shuttle molds from the end of the
mold tunnel to the beginning of the mold tunnel and one to drive
molds through the mold tunnel.
The mechanical drive system utilized by corrugator designs
in the prior art typically have mechanical drives comprised of
motors, gear boxes, gear reductions, transmissions, sprockets,
chains, idler sprockets, power take off shafts and other
mechanical drive systems. These drive methods and systems may
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require extensive maintenance. Furthermore, these drive methods
are subject to wear as many components are in direct contact with
one another. There is also the potential problem of backlash in
the driving mechanisms, which may be accentuated in the
propulsion of the molds.
The corrugators such as taught by U.S. Pat. Nos. 5,494,430;
5,645,871; and others are known as vertical style corrugators. A
forming mold tunnel is in line with the extrusion head die. The
non-forming (return) of the mold chain is typically overhead or
below the product center line. As shown in Figure 2 of U.S. Pat.
No. 5,494,430, the molds which are not in use in the mold process
are typically open and cannot be used in the manufacture of
product until they return to the forming side of the corrugator.
This results in a machine having a greater height in the vertical
plane and does not utilize the non-forming molds in production.
U.S. Pat. No. 5,257,924 teaches at least one method for using
multiple molding sections in a corrugator.
Maintaining a vacuum is another concern in many corrugator
and mold designs. U.S. Pat. Nos. 4,718,844 and 5,059,109 teach
at least two different vacuum configurations for mold blocks.
Thermoexpansion of forming molds can cause vacuum loss through
the vacuum interface during production. The vacuum interface is
typically a rigidly fixed device that interfaces with the molds.
If the interface is not complete, vacuum leakage will occur.
Although it appears that improvements have been made to the mold
blocks for maintaining vacuum, the interface with the vacuum does
not appear to have been thoroughly perfected.
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With the clam shell style mold carriers, the mold carriers
typically operate on an oval track. The radius on the curved
portions of the track typically is relatively large. This causes
a need for the extrusion die to be of relatively long length.
Longer dies have been found to create problems in the manufacture
of double walled tubing such as high head pressures and/or uneven
distribution of the extruding plastic. Furthermore, long die
lengths reduce the potential selection of materials to be
utilized which could otherwise be utilized with shorter die
lengths.
A need exists to utilize materials such as polyvinylchloride
(PVC). Polyvinylchloride (PVC) requires a shorter die length
than is available in many prior art corrugators.
When constructing some prior art corrugators, a mold chain
length has been fixed. If a customer has a special product, or
wants to increase or decrease the length of the machine, the
customer could typically expect extensive modifications to be
required and performed upon that particular corrugator. Today,
there is a high demand for greater and greater speed which often
results in longer and longer forming tunnels. For instance, when
a 20-foot mold section was once found adequate, a consumer now
may desire a 40-foot mold section. This modification may be
extensive and require a lengthy down time for the machine.
2 5 SUNE2ARY OF THE INVENTION
The present invention recognizes and addresses the foregoing
disadvantages, and others, of prior art construction and methods.
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Accordingly, it is an object of the present invention to provide
an improved machine, such as a corrugator, for making plastic
tubing or other formed plastic product. A trackway defining a
continuous path and a plurality of carriages for carrying mold
blocks about the continuous path are utilized. Each of the
carriages transports at least one pair of mold blocks which are
linearly displacable from one another. In a closed
configuration, a first and second pair element of a pair of mold
blocks engages with one another along a molding section of the
continuous path to form an axial portion of a mold tunnel in the
molding section. Using the linear closing mechanism, the molds
may be operated on a continuous path which has a quick, i.e.,
smaller, entrance radius. A small entrance radius in a
continuous path allows for extrusion dies to be shortened. With
a die of shorter length, the traditional problem of die length is
reduced. Accordingly, rapidly solidifying materials such as
polyvinylchloride (PVC) may be utilized to make corrugated
tubing.
The mold blocks open and close preferably using a non-hinged
carrier. This carrier is comprised of a main plate with two
linear slot bearings which are mounted in a manner to allow the
mold to open evenly away from the product. Accordingly, the
carrier need not hinge away from itself. The linear non-hinged
mold carrier, is preferably composed largely of "off-the-shelf"
components which may provide for quick field repairs without the
need to remachine mold locating surfaces. Furthermore, the
radius and angle of curvature of the continuous track may assist
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in correct positioning of opposing mold blocks when forming the
mold tunnel without having mold surfaces wear against one
another.
The mold blocks may be balanced by use of sprockets and
chain. Movement of one block may drive the opposing block in a
similar fashion (i.e., inward or outward). The balanced design
is believed to assist in prolonging the life of components and
may assist in faster production rates due to lower power
consumption.
In an alternative embodiment, linear motors operate in
conjunction with programmable logic controls to engage a select
number of carriages at the beginning of the mold tunnel to
continuously drive the carriages along the mold tunnel. The
linear motor working with programmable logic controls is also
able to shuttle carriages which are not in the mold tunnel along
portions of the continuous path at a higher rate of speed than
the speed of the mold blocks along other sections of the
continuous path. Linear motors may be used independently of
mechanical drive mechanisms such as gear boxes, chains,
transmissions, and the like. The linear motor may accelerate a
carriage which leaves the mold tunnel, shuttle the out-of-service
mold block through a second section of the continuous path,
decelerate the carriage prior to the beginning of the mold tunnel
and maintaining a predetermined speed, speeds, and/or positions
through the mold tunnel. The more preferable method of moving
the carriages is to use a drive rod and sprocket to drive at
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least one at a time with the driven carriage pushing the others
about the continuous loop.
The mold block may be utilized in conjunction with a vacuum
machine for molding tubes. In a preferred embodiment, the tube
product is corrugated. The mold block is preferably adapted to
moving about an endless path and cooperates with other blocks to
define a molding tunnel with a vacuum source along a portion of
the path. In an alternative embodiment, at. least two molding
tunnels may be formed at two different portions of the continuous
path.
The mold blocks may include a plurality of sub-blocks
secured end to end. Each sub-block has a face arcuate about a
longitudinal axis and corrugated with at least one complete wave
length of circumferential grooves and lands. A vacuum channel
within the mold block provides access from a vacuum source to the
interior portion of the mold. The vacuum passage is connected to
a vacuum source at a vacuum interface as the mold block passes
along the mold tunnel. The vacuum interface in the molding
section or sections preferably utilizes a cushion. This cushion
may be pneumatic or mechanical such as springs and allows for the
interface to adjust as the forming molds thermally expand without
binding or leakage.
The corrugator utilizes at least one molding section and may
include a shuttle section. In a transition section, a one or
more tracks direct the mold carrier and the mold blocks to a
closed position where they are maintained through a molding
section. A second transition section contains one or more tracks
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which may assist in guiding the mold blocks to an open position
to allow the extruded product to be removed. Preferably, the
tracks) and rollers prevent "sawtoothing" by properly aligning a
pair of mold blocks in a closed configuration during the molding
section.
Preferably the machine is constructed in a horizontal
fashion instead of a vertical planer fashion such that the molds
move in a horizontal fashion. The vertical profile is lowered by
not having two mold sets one above another. Furthermore, the
shorter profile allows easier accessability to the molds and
carriers for maintenance and changeover. Horizontal design may
also allow for increasing production requirements. If a
continuous mold chain is utilized instead of shuttling the molds
at a high rate of speed in nonforming sections, it is possible to
mold corrugators in two directions. Accordingly, a single
corrugator could have output coming from at least a first mold
tunnel and a second mold tunnel. Another advantage of the
horizontal design is the ability to quickly change mold blocks in
the carriers which allows a single corrugator to manufacture a
plurality of different products by swapping out the mold blocks
on the carriers.
The mold blocks may be cooled in a number of ways. The
traditional water cooling techniques may be utilized. Ambient
air cooling, such as may be achieved by passing the open mold
blocks through space when not molding, may also be utilized. If
this cooling is not sufficient alone, forced air cooling may also
be utilized. One method of forced air cooling includes the use
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of vortex nozzles. The vortex nozzles may be mounted in
locations which allow for optimum thermal transfer of heat away
from the mold. Utilizing cooling vortex nozzles, the traditional
method of water cooling within the mold blocks may be eliminated.
A second method of cooling which may be utilized includes
spraying the mold blocks with a solution (such as water or an
evaporable solution). Using this second method, the
thermodynamics of the heat of vaporization of the evaporating
substance is utilized to increase the efficiency of the cooling
process.
The corrugator of the preferred embodiment is also modularly
constructed in sections. These sections interlock with one
another. Accordingly, a single carrier design may be utilized
regardless of a particular configuration length needed. A
machine may be taken apart at a location, sections) inserted,
and the machine reconnected with the new section installed. In
this manner, a single machine may be configured for different
lengths or types of products. Modifications may be performed in
a short period of time. Also, parts of like machines can be
interchangeable. Furthermore, machines may be combined in tandem
for ultra high-speed production and then separated for standard
rate production. Modularity is also an advantage as components
can be sold directly to the customer for in-house changes.
Modularity allows for higher volume production of like parts
which may reduce the individual part costs.
Additional objects and advantages of the invention will be
set forth in part in the following description, or may be obvious
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from the description or accompanying drawings, or may be learned
through the practice of the invention.
The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate several
embodiments of the invention and together with the description,
serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
A full and enabling disclosure of the present invention,
including the best mode thereof and directed to one of ordinary
skill in the art, as set forth in the specifications, which makes
reference to the appended drawings in which.:
Fig. 1 is a top diagramatic view of a mechanically driven
embodiment of the invention;
Fig. 2 is a top plan view of an alternative embodiment of
the invention driven by linear motors;
Fig. 3 is a detailed side plan view of a preferred
mechanically driven embodiment of the invention with only tow
mold block assemblies shown;
Fig. 4 is a side diagramatic view of the machine of Figure 3
illustrating the formation of a mold tunnel by a plurality of
closed mold block assemblies;
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Fig. 5 is a front plan view of the machine of Figure 4 taken
along the line A-A showing a mold block in the open position, and
a mold block in the closed configuration;
Fig. 6 is a detailed front plan view of the machine of
Figure 3 showing mold blocks of two different sizes;
Fig. 7 is a side view of a mold block assembly of the
preferred embodiment with the mold blocks removed;
Fig. 8 is a top plan view of an alternative configuration
showing the use of two extruders;
Fig. 9 is a side plan view of a portion of the mold block
assembly of Figure 7 with a first mold block half installed;
Fig. 10 is a side plan view of a portion of the mold block
assembly of claim 7 with a larger mold block half installed;
Fig. 11 is a top plan view of the mold block assembly of
Figure 7 showing two top mold block halves mounted in a single
carrier; and
Fig. 12 is a side plan view of a portion of the mold block
assembly of Figure 7 with an adapter mounted with a quick release
mechanism.
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Repeat use of reference numerals in the present
specification represent like, similar or analogous parts,
structures or elements of the present invention throughout
several views.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference will now be made in detail to the presently
preferred embodiments of the invention, one or more examples of
which are illustrated in the accompanying drawings. Each example
is provided by way of explanation of the invention, not
limitation of the invention. In fact, it will be apparent to
those skilled in the art that modifications and variations can be
made in the present invention without departing from the scope or
spirit thereof. For instance, features illustrated or described
as part of one embodiment may be used on another embodiment to
yield still a further embodiment. Thus, it is intended that the
present invention covers such modifications and variations as
come within the scope of the appended claims and their
equivalents.
Referring to Figure 1, a machine 10, in the form of a
corrugator is illustrated. The machine 10 is cooperable with a
first extruder 12 to continuously mold an extrudable material
such as a plastic. The machine 10 utilizes at least one
continuous path 14 which is preferably located on machine 10. A
plurality of separate carriages 16 carry mold blocks about the
continuous path 14 of said machine 10. Each of the carriages 16
carries at least one pair of mold blocks, illustrated as mold
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block pairs 18. The mold block pairs 18 are displacable from one
another and are capable of mating engagement with one another
along a molding section 20 of the continuous path 14. When the
mold block pairs 18 are in mating engagement with one another and
closed to form a mold tunnel, plastic may be molded within to
form piping 22 or other products. The mold blocks move along the
continuous path 14 to enter the molding section 20 at its
beginning 24 and exit at the molding section end 26. The
preferred method of driving the carriages 16 about the continuous
paths 14 is to utilize a drive shaft 28 with spokes 30 which
engage at least one carriage 16 at a time. Since adjacent
carriages 16 are substantially adjacent to one another in the
preferred embodiment, all of the carriages 16 may be moved by
driving one or more of the carriages 16.
In an alternative embodiment, the machine 10 may utilize a
linear motor drive system as shown in Figure 2 which has at least
one stator 32 which is located proximate to the continuous path
14. Rotor elements 34 which are connected to the carriages 16 in
this embodiment. In some embodiments, it may not be necessary to
have a rotor element 34 on every carriage 16, however, the
embodiment illustrated in Figure 2 has rotor elements 34 on every
carriage 16.
If linear motors are utilized, multiple stators 32 may be
required to propel the carriages 16 at different speeds along the
path 14. A control device 38 may be connected to a plurality of
stators 32 to achieve the desired changes of speeds in different
locations. Furthermore, sensors 40 may also be utilized along
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the continuous path 14 or at other locations to monitor position
of carriages 16 and mold block pairs 18 (collectively referred to
as mold block assemblies 36) and provide information to the
controller 38.
By using a higher speed at portions of the continuous path
14 where a particular mold block pair 18 is not in use in a
molding section 20, the carriage 16 may be shuttled to another
portion along the continuous path 14. This process would allow
for fewer mold block pairs 18 and mold block assemblies 36.
Fewer mold block pairs 18 and mold block assemblies 36could
result in a lower cost of the overall machine 10.
Also in the alternatively preferred embodiment illustrated
in Figure 2, connectors 42 link the control device 38 to stators
32. Furthermore, the control device 38 may incorporate an
electronic power supply device, and a computer or controller,
which may generate appropriate signals to the stator 32. The
signals may be the driving force which propels the mold block
assemblies 36 around the continuous path 14. Accordingly, the
requirement for mechanical drive devices such as chains to propel
the mold block assemblies 36 around the continuous loop 14 may be
eliminated in this embodiment. The positioning of connections 42
allows for the speed of the mold block assemblies 36 to be
adjusted at different locations along the continuous path 14.
Other locations and connections 42 may be necessary or desired
for particular applications. The control device 38 utilized to
control the speed of the mold block assemblies 54 preferably uses
"quick carrier return technology" which allows for the shuttling
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carriages 16 of unused mold blocks pairs 16 at a higher rate of
speed relative to the progress of mold blocks pairs 18 through
the mold tunnel 20.
Referring back to Figure 1, the machine 10 also has a vacuum
system which is supported by a vacuum support 44. The vacuum
support 44 houses a plenum which connects a vacuum source to a
vacuum interface. Figure 1 also shows a cooling technique using
a mister 46 and blower 48. Other details of the vacuum system
and cooling technique will be discussed below.
The machine 10 is constructed in a modular fashion. Figure
3 illustrates the frame 50 of the machine 10 in two sections:
first frame section 52 and second frame section 54 connected at
interface 56. First frame section 52 may be disconnected from
second frame section 54, the two spread apart and a third frame
section may be inserted to make the machine 10 larger. In the
alternative embodiment of Figures 2 and 4, a third frame section
58 and fourth frame section 60 are illustrated as having widths
from only about half that of a single mold block assembly 36 up
to that of about three mold block assemblies 36 and are connected
at junction 62. Utilizing smaller frame sections 58, 60 may
allow for more precise sizing of the continuous path 14.
Furthermore, as shown in Figures 1 and 2, a frame section 58 may
include first and second frame sub-sections 64, 66. Sub-sections
64,66 together include an entire width of the machine 10. The
sub-sections 64, 66 meet at interface 68. First, second, or
fourth sections 52, 54, 60 may also be comprised of such sub-
sections which permit the width of the machine 10 to be adjusted
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by the use of varied width subsections or spacers between
subsections. Accordingly, frame sections 52, 54, 58, 60 may be
as large or as small as needed for a particular application and
make the modular machine 10 easier to adapt to a particular need.
Furthermore, as illustrated in Figure 3, the machine 10 may be
disconnected at connection 70 and raised in the vertical
direction to accommodate taller carriages 16 or for other
modification reasons.
In Figures 1 and 3, first and second sections 52, 54 could
be disconnected at interface 56 in order to lengthen the machine
10. Accordingly, two continuous path portions of the first and
second sections 52, 54 and an inserted section (not shown) would
form a new longer the continuous path 14. Alternatively, in the
embodiment illustrated in Figures 1 and 2, other portions or
sections of the machine 10 may be removed to allow for shortening
of the machine 10 to accommodate a shorter mold tunnel 20 if
desired. By utilizing this manner of modular construction, the
length or shape of the continuous path 14 of the machine 10 may
be adjusted.
The continuous path 14 of the machine 10 is preferably
constructed in an oval shape. This shape has been found to
minimize the space required by the machine 10. Other
configurations may also be constructed. Sections of the
continuous path 14 of the frame 50 and the oval configuration
illustrated in Figure 1 have curved portions such as curved
portion 72. Curved portion 72 may have a semicircular or other
curved shape to transition the continuous path 14 from a first
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linear section 74 to a second linear section 76. The curved
section 72 may be utilized by itself or in conjunction with other
curved sections 72 to transition a first linear section 74 of the
continuous path 14 to a second linear section 76 of continuous
path 14. The preferred connection system for different portions
of the frame 50 is to utilize releasable connectors at the
interfaces or junctions of the frame sections. Pins and bores
may be suitable connectors. A pin may be anything which fits
within a cavity of the frame 50 such as a bolt or dowel.
Details of the machine 10 have been omitted from many of the
figures in order to clearly illustrate the invention. However,
it should be understood that such details are not directly
relevant to the concept of the present invention, and that
different types of machines could also incorporate the present
invention. For example, when the illustrated embodiment uses a
vacuum to conform an extrudable material, such as plastic, to the
mold blocks as described in detail hereafter, the present design
could be used with different mold blocks, etc., or could even be
used with a corrugator structure which uses different means, such
as internal pressure, to conform the plastic to the mold blocks.
In the alternative embodiment of Figure 5, the mold block
assemblies 36 are illustrated as being driven about a path in the
form of a trackway 78. The trackway 78 is preferably
horizontally oriented, that is, the mold block assemblies 36 are
carried by the trackway 78 for movement in a substantially
horizontal plane (i.e., parallel to the floor where the machine
10 is located). The trackway 78 of the preferred embodiment is
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illustrated in Figures 3 and 5. The trackway 78 provides a
support for the carriages 16 as they traverse about the
continuous path 14. It is preferred that the trackway 78 support
a large portion of the weight of the carriages 16 which is
believed to assist in extending the longevity of the machine 10
while providing for faster rates of production. Additionally,
the two sizes of mold block pairs 18, 80 illustrated in Figure 3
are for illustrative purposes. Although different size mold
blocks 18, 80 could be utilized during product formation, a
transition between sizes would be required. For the production
of corrugated piping, mold block pairs of a single size are
typically utilized.
An extruder 12 is provided adjacent to the beginning of the
mold section 20 and, in the alternative embodiment of Figure 8,
extruders 12, 82 are provided for the machine 10 and two mold
tunnels: a first mold tunnel 20 and a second mold tunnel 84.
These two mold tunnels 20, 84 have extruders 12, 82 adjacent
thereto. The extruder 12 or extruders 12, 82 may or may not be
connected to the frame 50 in some manner.
It is contemplated that at least portions of an extruder 12
may be moved back and forth toward and away from the beginning of
the associated mold section 20. For instance, as illustrated in
Figures 3-6, the frame 50 may include rollers 86 which allow the
machine 10 to be moved relative to a stationary extruder 12. In
the preferred embodiment, the rollers 86 are located on one or
more tracks 88 which allow a single operator to move the machine
10 relative to the extruder 12. Movement of the machine, or an
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extruder 12 may be necessary during start up and shut down of the
machine 10. Alternatively, moving portions of an extruder 12 or
frame 50 may be necessary for maintenance.
In most applications, the material to be extruded, normally
a plastic, is heated to the desired temperature and forced into
the nozzle of the extruder 12. The machine 10 is then rolled
into position with the extruder nozzle extending into the mold
tunnel 20. A plurality of adjustment mechanisms 90 preferably
operated by cranks 92 are utilized to provide for precise
positioning of the machine 10 relative to the extruder 12.
Cranks 92 are preferably hand wheels, but automated equipment
could also be utilized such as electric servos or stepper motors,
especially if the machine 10 is equipped with a sophisticated
control device 38 that may also control these motors. Care
should be taken for the extruder nozzle to not contact the mold
blocks 18 in the mold tunnel 20 during extrusion as aluminum mold
blocks 18 would be easily damaged. Accordingly, the adjustment
mechanisms 90 allow for very precise adjustment of the mold
tunnel 20 relative to the frame 50. Specifically, the adjustment
mechanisms 90 may allow for in excess of two inches of movement
vertically at either end of the frame 50 in very minute
increments as well as in excess of two inches of movement
laterally at the mold tunnel beginning 24 and end 26. Stops 94
illustrated in Figure 3 are utilized to located the machine 10
relative to the extruder nozzle, and adjustment mechanisms 90 are
also utilized to adjust the distance of the mold tunnel beginning
24 from the extruder nozzle.
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Figure 6 shows the vacuum frame 44 supports ducts 45 which
are provided along the mold tunnel 20. The ducts 45 communicate
with a manifold 47 in the mold block pairs 18 as described
hereafter to draw a vacuum around the outside of the extruded
material in the molding sections 20.
A plurality of mold block assemblies 36 are supported and
guided by the trackway 78 for rolling action thereon.
Preferably, all mold block assemblies 36 are alike on any
particular machine 10.
Regarding the mold assembly 36 of the embodiment shown in
Figure 5, each mold block assembly 36 has a carriage 16 which
supports the pair of mold blocks 18. The carriage 16 is
supported on rollers 98, 100 which may be a portion of the
carriage 16 or may be a portion of the trackway 78, as
illustrated in this embodiment. Additional support for the mold
block assemblies 36 may be provided by rollers 102, 104.
Furthermore, raceways, tracks or bearings 106 may be utilized to
maintain the carriage 16 in its proper location along the
trackway 78. The rollers 98-104 and bearings 106 may be utilized
to enable the mold block assemblies 36 and more particularly the
carriages 16 to roll along the trackway 78 without derailing or
excessive resistance.
To maintain the mold block pairs 18 of the mold block
assemblies 36 in alignment and to assure that the carriages 16
roll properly within the trackway 78, raceways 108-118 are
provided along the trackway 78. The raceways 108-118 assist in
the opening and closing of the mold block pairs 18. The mold
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block pair 18 has a first mold half 120 and a second mold half
122. The first and second mold block halves 120, 122 are
substantially mirror images of each other, and each is an open
ended semi-cylinder having a corrugated inner wall formed by
alternating grooves and lands.
Referring back to Figure 5, the mold block pair 18 on the
left is closed as it is positioned while in molding section 20
and forms internal passage 202. Rollers 102, 104 are contacting
raceways 108, 110 which assist in maintaining the mold block
halves 120, 122 next to one another. The mold block pair 18 on
the right is open. Raceways 112-118 are further apart than
raceways 108, 110 and maintain the block halves 120, 122 in an
open configuration relative to one another. Referring to Figures
3 and 4, transition segments 130-136 move the mold block pairs 18
or 80 relative to the carriage 16 by acting on rollers 102, 104.
As a mold block pair 18 enters transition segments 130, 132
(from left to right in Figure 4) the rollers 102,104 direct the
mold blocks to move from the open position illustrated to the far
left to a closed position as illustrated along mold tunnel 20.
At the end of the mold tunnel 20, transition segments 134,136 act
on rollers 102,104 to direct the mold blocks to an open position
as illustrated on the far right, thereby allowing product to be
removed from the machine 10.
The mold frames, or holders 138, 140 are connected to a
linear guide segment 142 with bearings, such as linear bearings
168 so that the mold halves 120, 122 open and shut at the
transition sections 130-136 as illustrated in Figures 3 and 4.
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In the preferred embodiment, the transition segments 130, 132
include a portion of the curved segment 72 at the ends of linear
segments 74,76. In fact, although the majority of the curved
segment 72 may have a relatively small radius such as about two
or three feet, it has been found helpful to have a large radius,
such as about twenty to twenty five feet at. or near end portions
of the transition segments 130, 132 so that. adjacent mold block
pairs 18 come together without imposing substantial wear on the
touching end portions of adjacent mold blocks as they contact to
form the molding section 20. Utilizing the linear travel of the
mold block halves 120, 122 to close, the radius of curvature in
the curve portions of the frame 50 may be made smaller than is
common in the prior art for hinged type mold blocks. The use of
raceways 130, 132 to close the mold block pairs 18 from an open
position allows for a relatively quick closing of the mold blocks
120,122. Accordingly, by reason of the shorter radius of
curvature and quicker closing, a shorter die may be utilized. A
shorter die allows the use of rapidly setting materials such as
polyvinylchloride (PVC) which have not traditionally been deemed
suitable in these machines 10. Other methods may also be
utilized to open and close the mold block halves 120, 122,
instead of or in addition to raceways 108-118 acting on directors
or rollers 102, 104.
Referring to Figures 6 and 7, the mold block assembly 36 has
carriage 16 which includes rollers 104, 106 for cooperating with
trackway 78. Although only two rollers 104, 106 are shown in
Figure 6, it is anticipated that four or more rollers 104, 106
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will be utilized with each assembly 36 in order to provide more
stability to the assembly 36 along the trackway 78 as illustrated
in Figure 7. The rollers 104, 106 are preferably eccentric cam
rollers, like almost all of the rollers in the preferred machine
10, which allow for precise adjustment of the rollers 104, 106 to
ensure that the assembly 36 is balanced and properly oriented to
reduce vibrational tendencies and move the mold block pairs 18 in
a smooth fashion through the continuous loop 14.
Referring to Figure 6, rollers 148-154 are located on the
ends of the carrier 16 to cooperate with runs 107, 108, or
raceways in a slightly different fashion than shown in Figure 5.
These rollers 148-154 maintain the carrier 16 in the runs 107,
108 and assist in moving the assemblies 36 about the continuous
path 14. Additionally, in the preferred embodiment, two of each
of the rollers 148-154 are utilized to assist in stabilizing the
carrier 16.
The assembly 36 is illustrated in Figure 7 without the mold
block halves 120, 122 and in an open position. An upper and a
lower mold holder 138, 140 are spread apart, in an open position.
The upper and lower mold holder 138, 140 may be a portion of the
mold block halves 120, 122, or more preferably, an element with
connectors to hold a mold block half 120, 122 thereto. A mold
block frame 160, 162, shown in Figure 6, may be necessary in some
embodiments to connect the holder 138, 140 to the mold block
halves 120, 122. A plurality of different embodiments are
illustrated in Figures 9-12 illustrating different configurations
of mold block halves 120, 122 and frames 160, 162.
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Referring back to Figure 7, the preferred embodiment
includes connected upper and lower holders 138, 140 through a
coupling such as a sprocket 164 connected to a chain 166. The
holders 138, 140 have linear bearings 168 which cooperate with
linear guide 142 which assist in the opening and closing of the
mold halves 120, 122. In the illustrated embodiment, the
coupling connects the movement of the halves 120, 122 so that
when one of the two holders 138, 140 is moved either inwardly or
outwardly, the other holder 138, 140 will move in a similar
fashion (inwardly or outwardly). A linkage arm 170 allows for
adjustment of the amount of tension of the chain 166. Gravity
acting on the lower holder 140 will tend to keep the two holders
138, 140 apart unless the top holder 138 is driven inwardly by
the roller 102 riding through the transition 130. This will
drive the upper holder 138 inwardly, toward a center of the
carrier 16. The chain and sprocket system will pull the lower
holder 140 inwardly as well. This brings the facing surfaces
121, 123, 125, 127 of the mold block halves 120,122 together.
The lower transition raceway 132 and roller 104 may not be
necessary in all embodiments as a result of the chain 166 and
sprocket 164 system, however the lower roller 104 and transition
raceway 132 are utilized in the presently preferred embodiment.
Figures 9-12 show the mold block assembly 36 in more detail.
The rollers 148,152 travel along tracks or raceways 156, shown in
Figure 6. The roller 102 is located in mold positioning raceways
such as transitions 130-136 shown in Figure 3, which assist in
opening and closing the mold block holders 138, 140. The
CA 02317871 2000-09-08
transitions 130-136 and raceways 108-118, also shown in Figures 3
and 5, determine the position of the mold blocks 120, 122
relative to one another as a particular carriage 16 travels
around the continuous path 14. Linear bearings 168 slide on
guides 142 to allow vertical movement of the mold block pairs 18.
Figure 9 shows a first mold block 172 with a two arms 174,
176 comprising the frame 160. The arms 174, 176 connect the mold
block 172 to the holder 138 at connections 178, 180. Connector
180 is a dovetail to dovetail slide fit while connector 178 is
preferably a bolt or other connection. By removing connector
178, the friction fit of connector 180 is relieved and the mold
block 172 may be pulled up and off the holder 138.
Figure 10 is a mold block assembly 36 with an alternative
mold block 182. Due to the size of this mold block 182, the
connectors may restrain the mold block 182 without the need for a
frame 160 as arms 174, 176 as illustrated in Figure 9. Obviously
a larger diameter corrugated pipe product may be manufactured
with the mold block 182 of Figure 10 than with the mold block 172
of Figure 9.
Figure 12 is a mold block assembly 36 with an adapter 184.
The adapter 184 may be a portion of frame 160 and has a release
lever 186 instead of connection 178 in order to assist in
connecting a third mold block design 188 to the holder 138. The
mold block 188 connects to the adapter 184 at connections 190,
192 which may, or may not be similar to connections 178, 180 of
Figure 9. The adapter 184 connects to the holder 138 at
connections 180, 194 and release arm 186 may allow for rapid
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removal of block 188. The release 186 is designed to allow rapid
replacement of mold blocks, as for instance, any of mold blocks
172, 182, 188 with other mold blocks so that a single machine 10
may be utilized with a variety of blocks by the manufacturer.
Instead of needing two machines to make two different size or
type products, a single machine 10 with multiple sets of mold
blocks, such as blocks 172, 182, 188 may be utilized. Almost any
mold block pair of any manufacturer may be configured with an
adapter 184 for use with the machine 10 of the preferred
embodiment.
Figure 11 is a top view of Figure 12. Two or more blocks
188 may be utilized with a single mold block assembly 36
depending on the width of each pair of mold blocks 188. For
larger and wider blocks 182, one pair of blocks per assembly 36
would likely be more common. Common sizes are four inch widths
and eight inch widths. When constructing blocks 18 in standard
size widths, one will see the versatility of being able to
quickly swap out mold blocks of different sizes in rapid order, a
feature of at least some embodiments of the present invention.
One machine 10 can be modified in a relatively small period of
time to change the product produced.
Figure 11 also shows the relationship of receiver walls 196,
198 which bound a receiver 200 of the mold block assembly 36.
This receiver 200 accepts the spoke 30 connected to the drive
shaft 28 (shown in Figure 1) when at the correct position in the
continuous path 14. The drive shaft 28 and spokes 30 illustrated
in Figures 1 and 6 to move the mold block assemblies 36 about the
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continuous path 14. Electric motor 128 drives the drive shaft 28
which moves the spokes 30. The spokes 30 cooperate with the
receivers 200 (illustrated in Figure 11) in the mold block
assemblies 36 to move at least one assembly 36 at a time. Since
the preferred embodiment includes a continuous chain of
assemblies 36, the driven assemblies 36 push the non-driven
assemblies 36 about the continuous path 14.
Alternatively, each mold block assembly 36 may have a rotor
34 of a linear motor connected, integrally or otherwise thereto
on the carriage 16. The rotor 34 acts in conjunction with the
stator 32 in order to drive the mold block assembly 36 along a
continuous path 14 and trackway 78. Other connections for the
rotor 34 to the mold block assembly 36 could also be used.
As is shown in Figure 5, the mold block halves 120,122
include a passageway for connecting the internal mold tunnel 202
with the vacuum manifold 96, the passageway normally defined by a
plurality of slits in the lands intersecting axial bores in the
mold blocks 120,122 where the bores are connected by an annular
groove 119 in the mold blocks 120,122. The vacuum manifold 96
connects with vacuum interface 204 which is preferably attached
to vacuum manifold 96. The vacuum interface 204 is preferably
mounted with a cushion such as pneumatic cushion 206. Other
cushioning devices such as spring type mechanisms could be
utilized to maintain the vacuum interface 204 in contact with the
vacuum manifold 96 of the mold block pair 18 in the molding
section, 20. The pneumatic cushion 206 is able to adjust to
expansion of the mold block pair 18 without binding or leakage.
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Furthermore, the pneumatic cushion 206 may adjust for other
movement of the vacuum manifold 96. The vacuum cushion 206 need
not be located upstream of the vacuum interface 204 but could
even be incorporated as part of the vacuum interface 204.
Preferably, the vacuum frame 44 supports the cushion 206, the
vacuum interface 204 and the manifold 96. An internal portion of
the vacuum frame 44 provides a channel or duct 45 for connecting
a vacuum source (not shown) to the vacuum interface 204. In this
manner, a vacuum may be drawn in the mold tunnel 202.
It should be understood, however, that still other mold
block structures could be used within the scope of the present
invention. For example, other air and vacuum systems both
internal and external of the mold blocks could be utilized such
as those taught by U.S. Pat. Nos. 5,257,924; 4,718,844; and
5,059,109.
As shown in Figure 2, cooling of mold blocks 18 may be
accomplished by cooling nozzles 208 positioned around the mold
block assemblies 36 or even within the frame 50 to cool mold
block pairs 18. The location of the cooling nozzles 208 are in
areas such that the mold block pairs 18 may be reduced in
temperature by blowing forced air on the mold blocks 18 at
specific locations. A single cooling nozzle 208 may be utilized
or multiple cooling nozzles 208 may be utilized at various
locations. A sufficient quantity of cooling nozzles 208 may be
employed to cool the mold blocks 18 so that internal cooling
water systems of the mold blocks is not necessary. This
significantly reduces the cost and complexity of mold block
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assemblies 36 and mold blocks 120,122. Other cooling air systems
such as the system taught in U.S. Pat. No. 5,257,9924 could also
be utilized.
Another method of cooling which may be utilized is shown in
Figure 1 and includes spraying the mold blocks with a solution
(such as water or an evaporable solution) with mister 46. It is
preferred that external portions of the mold blocks 18 be sprayed
with in relatively small amounts of solution. The liquid may be
heated to bring the liquid closer to the temperature where it
would evaporate or turn into a gaseous form. As the solution
evaporates, a large amount of energy in the form of heat is
removed from the mold blocks 18. Since most mold blocks 18 are
aluminum, the heat quickly transfers from the hotter internal
portions of the mold block 18 to the external sprayed portions
for energy removal. A vent 48 including a blower may be utilized
to direct the high moisture air away from the work area to
maintain a proper level of moisture content in the ambient air.
This reduces the likelihood of rusting other portions of the
machine 10. Additionally, additives may be added to the
solution, including oils, to reduce the possibility of rust.
Using this evaporative cooling method, the thermodynamics of the
heat of vaporization of the evaporating substance is utilized to
increase the efficiency of the cooling process. The vertical
orientation of the mold blocks 120,122 facilitates spraying the
external surfaces with an evaporating solution without
contaminating the internal molding surfaces.
CA 02317871 2000-09-08
Numerous alternations of the structure herein disclosed will
suggest themselves to those skilled in the art. However, it is
to be understood that the present disclosure relates to the
presently preferred embodiments of the invention which are for
purposes of illustration only and not to be construed as a
limitation of the invention. All such modifications which do not
depart from the spirit of the invention are intended to be
included within the scope of the appended claims.
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