Note: Descriptions are shown in the official language in which they were submitted.
CA 02206277 2000-11-29
WO 96/16784 PCT/US95I14194
MULTIAXIS ROTATIONAL MOLDING
METHOD, APPARATUS AND STRUCTURE
This invention relates to a novel molding method and
apparatus and more particularly relates to a new multiaxis
rotational molding method and apparatus.
The production of man-made plastic and resin articles is an
industry that utilizes a high degree of automatically controlled
continuous processing. However, for units of appreciable size,
batch processing still is the rule rather than the exception. For
example, in the production of fiberglass structures such as boats,
it is customary to construct the hulls by hand. A plurality of
resin and fiberglass layers are sequentially laminated on an open
mold or a plurality of mixed resin/chopped fiber coatings are
applied over the mold.
Such hand building procedures require a great amount of
labor, supervision and continuous inspection to insure that a
reasonable level of quality is achieved. This greatly increases
the cost of the product.
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The applicant's earlier patents listed above provide a novel
method and apparatus for producing both large and small molded
structures continuously. The apparatus includes unique
combinations of components to produce a wide variety of different a
products. Achieving this capability requires a major capital
investment. Also, personnel to utilize the broad parameters of
the apparatus normally are highly trained and experienced.
The present invention provides a novel molding method and
apparatus which not only overcome the deficiencies of present
technology but also provide features and advantages not found in
earlier expedients. The multiaxis rotational molding method and
apparatus of the invention provide a means for the production of
a large number of uniform high quality products rapidly and
efficiently.
The multiaxis rotational molding apparatus of the present
invention is simple in design and can be produced relatively
inexpensively. Commercially available materials and components
can be utilized in the manufacture of the apparatus. Conventional
metal fabricating procedures can be employed by semi-skilled labor
in the manufacture of the apparatus. The apparatus is durable in
construction and has a long useful life with a minimum of
maintenance.
The apparatus of the invention can be operated by individuals
with limited mechanical skills and experience. A large number of
high quality molded structures can be produced rapidly by such
persons safely and efficiently with a minimum of supervision.
The molding method and apparatus of the invention can be
modified to mold a wide variety of new structures. Variations
both in product configuration and composition can be attained
simply and conveniently with the method and apparatus of the
invention. Even with such variations, uniformity and quality of
product dimensions and shapes still are maintained without
difficulty.
A novel method of the present invention for continuously
forming integrally molded structures includes the steps of
rotating a plurality of multisection mold assemblies about a
plurality of axes. A supply of a first freshly formed
polymerizable mixture is indexed into alignment with a first mold
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assembly. The first polymerizable mixture is flowed over surfaces
of a first enclosed mold cavity within the first mold assembly.
The flowing of the first mixture over the first mold cavity
surfaces and formation of a first resin therefrom are monitored.
The supply of the first polymerizable mixture then is indexed
' into alignment with an adjacent second mold assembly. The first
polymerizable mixture is flowed over surfaces of a second enclosed
mold cavity within the second mold assembly. Simultaneously
therewith, a supply of a second freshly formed polymerizable
mixture is indexed into alignment with the first mold assembly.
The second polymerizable mixture is flowed over the first resin
within the second mold assembly. The flowing of the first and
second mixtures within the first and second mold cavities and
formation of first and second resins therefrom are monitored.
The supply of the first polymerizable mixture next is indexed
into alignment with an adjacent third mold assembly. The first
polymerizable mixture is flowed over surfaces of a third enclosed
mold cavity within the third mold assembly. Simultaneously
therewith, the supply of the second polymerizable mixture is
indexed into alignment with the second mold assembly. The second
polymerizable mixture is.-bowed over the first resin within the
second mold assembly. The flowing of the first and second
mixtures within the second and third mold cavities and formation
of first and second resins therefrom are monitored.
The indexing of the supplies of the first and second
polymerizable mixtures into alignment with succeeding mold
assemblies and the flowing of the mixtures into the respective
mold cavities is continued until all of the mold assemblies have
received the mixtures. Also, the indexing and flowing of the
mixtures and the formation of resins therefrom are monitored.
The rotation of the mold assemblies is continued throughout
the steps of the continuous molding operation while monitoring
individually each axis rotation of the mold assemblies. The
monitored indexing and flowing of each mixture and the monitored
formation of each resin are coordinated with each monitored axis
rotation in a preselected profile to form the integrally molded
structures of the first and second resins.
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The mold sections of each mold assembly are separated after
the integrally molded structure therein has achieved structural
integrity within the mold cavity. The structure is removed from
the separated mold sections and the steps are repeated to form a '
multiplicity of the molded structures on a continuing basis.
Advantageously, solid particles are introduced into the mold
cavity of each mold assembly and the particles distributed in a
preselected configuration before indexing the supply of the first
polymerizable mixture into alignment with the respective mold
assembly. Also, the flowing of at least one of the polymerizable
mixtures into the mold cavity may be accomplished through a
delivery conduit while it is being withdrawn through the mold
cavity.
Preferably, each mold assembly is transferred to an adjacent
mold receiving station prior to separating the mold sections and
returning the mold assembly to a molding position for repeating
the methad of the invention. A plurality of mold assemblies may
be provided for each molding position so molding can continue
while other mold assemblies are being opened and being prepared
for another molding cycle. Cavity changing inserts may be
positioned into the mold cavity while the mold sections are
separated.
Benefits and advantages of the novel multiaxis rotatable
molding method and apparatus of the present invention will be
apparent from the following description and the accompanying
drawings in which:
Figure 1 is a side view of one form of multiaxis rotational
molding apparatus of the invention;
Figure 2 is a fragmentary top view of the molding apparatus
shown in Figure 1;
Figure 3 is an enlarged fragmentary side view of the mixing
and molding portions of the molding apparatus shown in Figure 1;
Figure 4 is a further enlarged view in perspective of a mold
assembly of the molding apparatus shown in Figure 1;
Figure 5 is a fragmentary side view of another form of
multiaxis rotational molding apparatus of the present invention; '
and
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Figure 6 is a left end view of the molding apparatus shown
in Figure 5.
As shown in Figures 1-4 of the drawings, one form of
' multiaxis rotational molding apparatus 11 of the present invention
includes a support portion 12, a molding portion 13, a mixing
portion 14 and a control portion 15.
The support portion 12 of the multiaxis rotational molding
apparatus 11 of the invention includes a plurality of arm members
17,18,19,20 disposed in a generally horizontal orientation. One
end 21 of each arm member 17-20 extends from an upstanding frame
section 22. Advantageously, the upstanding frame section 22
includes a central upstanding section 23 from which the arm
members extend radially as shown in the drawings.
The molding portion 13 of the rotational molding apparatus
11 includes a plurality of mold supporting assemblies 26. One
mold supporting assembly is rotatably mounted adjacent a free end
24 of each arm member 17-20. Each mold supporting assembly 26
includes an independently rotatable mold connector section 27.
Each mold supporting assembly also includes acentral passage 28
therethrough. The central passage extends from a rotatable
connection 29 with the respective arm member and through the mold
connector section 27.
The mold connector section 27 preferably includes spaced
support sections 30 disposed along central passage 28
therethrough. Each arm member 17-20 advantageously also may
include one or more pivotal connections 31 along its length.
The molding portion 13 further includes a plurality of mold
assemblies 32,33,34,35. Each mold assembly includes a plurality
of separable mold sections 36 forming a substantially enclosed
mold cavity 37. As shown in Figure 4, mold sections 36 may
include plate sections 38.
The plate sections may be substantially flat or may be of
another configuration such as corresponding to that of a product
being molded. The plate sections may include cavity surfaces
with wear resistance, lubricity and/or other special properties
with or without underlying foam as may be formed with the method
of the invention.
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Connecting means e.g. electromagnets 39 selectively secure
the mold sections together. Also, connecting means 40 secure the
assembled mold sections to mold connector section 27.
Advantageously, mold sections 36 include flanges 42 '
overlapping adj acent sections . Sections 36 may include an opening
43 therethrough which may be disposed concentrically with a
delivery conduit 44 (Figure 3) during the molding operation. The
delivery conduit preferably is capable of being withdrawn from the
mold cavity 37 at a preselected rate.
A short tubular member advantageously may be affixed within
an opening 43. The tubular member may function as a funnel 45
(Figure 3) to facilitate introduction of material into the mold
cavity. ,Also, a tubular member may interconnect with a similar
tube 46 (Figure 4) in an adjacent structural unit to provide
communication between cavities of assembled structures.
The mixing portion 14 of the multiaxis rotational molding
apparatus 11 of the present invention includes a plurality of
closely spaced elongated enclosed mixing chambers 47,48,49. The
mixing chambers are mounted in a generally vertical orientation
on horizontal beams 50 extending from frame section 22. The
mixing chambers and the mold assemblies are mounted for relative
movement therebetween.
Each mixing chamber 47-49 includes an upper liquid mixing
section 51 with a first rotatable mixing element 52 disposed
therein. Each mixing chamber also includes a lower liquid/solid
particle mixing section 53. The lower mixing section 53 is
disposed below the upper mixing section 51. The lower mixing
section 53 is connected to the upper mixing section at an obtuse
angle.
A solid particle feeding hopper 54 is connected to the lower
mixing section 53 at a point thereon above its connection with the
upper mi~s:ing section 51. A second open rotatable mixing element
55 is disposed within the lower mixing section.
Advantageously, the mixing chambers 47-49 include separable
housing sections 57 to facilitate cleaning thereof. If desired,
the mixing portion also may include a solid particle feeding
hopper 60 which is operable independently of the mixing chambers
47-49. As shown in the drawings, the molding apparatus 11
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preferably includes mold assembly receiving stations 61 adjacent
each arm member 17-20.
The control portion 15 of the molding apparatus 11 of the
present invention includes actuating means including drive means
64,65 for each mold assembly. One drive means 64 rotates each
mold supporting assembly 26 and the mold assembly 32-35 affixed
thereto. Another drive means 65 rotates each mold supporting
assembly 26 and the mold assembly affixed thereto along an axis
generally perpendicular to the axis of rotation achieved with
drive means 64. Other drive means may be provided for opening,
closing, transferring mold assemblies, driving mixing elements,
etc. as required.
The control portion 15 also includes programmable memory
means 67, coordinating means 68, monitoring means 69 and circuitry
therefor. The drive means 64,65 advantageously include gear
motors, chains and sprockets connected thereto. Preferably, the
gear motors are variable speed motors. The actuating means may
activate other components such as pumps, valves, drives,
electromagnets, etc. Preferably, the monitoring means 69 includes
optical fibers 72 extending through the mold sections 36 as shown
in Figure 4.
The coordinating means 68 advantageously includes a process
controller 70 that initiates changes in the f lows of materials and
speeds of drives for each mold assembly to bring variations
therein back to the respective rates specified in the programs
present in the memory 67. This coordination commonly is achieved
through the transmission of information such as digital pulses
from the monitors and/or sensors at the control components to the
process controller 70.
The operating information is compared with the preselected
programming parameters stored in the memory 67. If differences
are detected, instructions from the controller change the
operation of the components to restore the various operations to
a
the preselected processing specifications.
in the use of the multiaxis rotational molding apparatus 11
of the present invention, the designs of the structures desired
first are established. Then, each design is programmed into the
memory 67.
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To start the operation of the apparatus 11, buttons and/or
switches of a control panel (not shown) are depressed to activate
the memory 67 and the other components of the control portion 15.
The coordinating means 68 energizes drive means 64,65. '
Also, monitors 69 and pumps, valves, etc. (not shown) are
energized by the coordinating means 68 in the preselected
sequences of the program stored in the memory 67. This causes the
raw materials in reservoirs 80,81,82 to advance along inlet
conduits toward the respective mixing chambers 47-49 located
above each of the arm members 17-20 of the molding apparatus 11.
For example, to mold a structure including a polyurethane resin,
reservoir 80 may contain a liquid reactive resin forming
material, reservoir 81 a particulate solid recyclable material and
reservoir 82 and other reservoirs - colors, catalysts, etc. as
required.
To produce high quality molded structures of the invention,
it is important that the raw material delivered to each mixing
chamber be uniform in volume and composition. This can be
facilitated by providing a continuous flow of raw materials to
each mixing chamber and the immediate transfer of each mixture
therefrom onto the cavity surface of a mold assembly 32-35.
However, the volume of the mixture delivered will vary
depending upon the particular incremental area being covered at
any instant. Also, the delivery to a particular mold assembly will
be terminated completely when a molded structure is being removed
from that assembly.
Advantageously, a separate bypass conduit (not shown) is
utilized from the end of each inlet conduit at a point adjacent
a particular mixing chamber back to the respective reservoir.
This construction provides for the delivery of a freshly formed
uniform mixture.from each mixing chamber even though the distance
is considerable between the reservoirs and the mixing chambers
which are located adjacent the mold assemblies. The control
portion 15 coordinates the operation of the various system
components so the required formulation flows onto the desired
areas of a particular preselected mold cavity. '
Rotation of each mold assembly 32-35 about an axis concentric
with that of mold connector section 27 and rotational movement of-
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the mold assembly about a second axis perpendicular to its
concentric axis are started and continue while each freshly formed
polymerizable mixture is transferred from a particular mixing
chamber into each preselected cavity 37 of a mold assembly. The
multiple axis rotational movement and any arcuate movement are
- continued to complete the f low of the mixture over all areas being
covered within a particular mold cavity. All movements are
controlled within the parameters stored in the memory 67.
For particular structures, the movements about the respective
axes may be continuous and/or intermittent at changing rates.
Also, it may be desirable to provide arcuate rotation, that is,
movement about an arc such as a rocking motion. Monitors 69
located within each mold assembly 32-35 signal the process
controller 70 when each polymerizable mixture has been distributed
over the preselected areas of the respective mold cavity so the
controller can initiate the next step of the molding method.
With the control components of the molding apparatus 11
activated, a first mixing chamber 47 is indexed into alignment
with the first mold assembly 32. The first freshly formed
polymerizable mixture flows from the mixing chamber into mold
cavity 37 and flows over the cavity surface and a first resin
layer is formed therein. The flowing of the first mixture over
the cavity surfaces and formation of a first resin therefrom are
monitored.
Thereafter, the first mixing chamber 47 is indexed into
alignment with an adjacent second mold assembly 35 and the first
polymerizable mixture flowed into the mold cavity thereof.
Simultaneously therewith, a second mixing chamber 48 is indexed
into alignment with the first mold assembly 32 and the second
polymerizable mixture therein is delivered into the mold cavity
of the first mold assembly 32 flowing over the first resin formed
in the cavity. The flowing of the first and second mixtures
within the first and second mold cavities and formation of a first
and second resin therefrom are monitored.
Thereafter, the first mixing chamber 47 is indexed into
alignment with a third mold cavity of an adjacent third mold
assembly 34 and the first mixture therein flowed over the cavity
surfaces. Simultaneously therewith, the second mixing chamber 48
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is indexed into alignment with the second mold cavity of the
second mold assembly 35 and the second mixture flowed over the
first resin formed therein. The flowing of the first and second
resins and formation of a first and second resin therefrom are
monitored.
The indexing of the first and second mixing chambers 47,48 '
as well as mixing chamber 49 and solid particle hopper 60 into
alignment with each mold assembly and the flowing of each mixture
into each mold cavity of any additional mold assemblies is
continued until all of the mold assemblies have received the
mixtures according to the preselected molding parameters. The
monitoring of the mixture flow, resin formation and mold assembly
rotation is continued throughout the molding operation as well as
the coordinating of this operating information with the
I5 preselected program profile.
When a molded structure within a mold cavity is sufficiently
cured that it possesses structural integrity, rotation of the
respective mold assembly is stopped and the mold assembly is
transferred to an adjacent mold receiving station 61 with hoist
means 62. The mold sections 36 are separated to free the
structural unit.
The molded structure then may be set aside to complete the
curing of the resin therein. During this period, the molded
structure, free of the mold' s restraint, stresses the high density
outer skin or layer. This stressing of the skin increases the
strength and puncture resistance thereof and also the structural
strength of the unit itself.
The mold sections 36 are prepared for another molding cycle.
This may include changing the position of one or more mold
sections with respect to each other, the substitution of mold
sections with different configurations and the like. Also, cavity
changing inserts may be positioned against the plate sections, if
desired.
t
The mold sections 36 then are assembled together and secured
such as by energizing electromagnets 39. The mold assembly now
is ready for repositioning on the adjacent arm member when the
next mold. assembly is removed therefrom.
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Figures 5 and 6 illustrate schematically another farm of
rotational molding apparatus 86 of the present invention. The
apparatus provides for the arrangement of a plurality of molding
assemblies 87,88 in a straight line with mixing chambers 89,90
traveling from one mold assembly to the next along overhead tracks
' 91,92. In other respects, the apparatus may include components
similar to those of apparatus 11 as described above.
The polymerizable mixtures employed to produce the structures
of the invention are selected to be capable of reaction to form
the particular resin desired in the final structure.
Advantageously, the resin is a thermosetting resin such as a
polyurethane or polyester. Should a polyurethane be desired, one
reservoir 80,81,82 may contain an isocyanate and another reservoir
may contain a polyol. More commonly, the reservoirs may contain
different partially formed materials which upon mixing interact
to form the desired polyurethane. Examples of such partially
formed materials include so-called "A stage" resins and "B stage"
resins.
Other resin forming systems may utilize a resin forming
material in one reservoir and a catalyst in a second reservoir.
Additional components can be pre-mixed with one of 'the resin
formers, e.g. fillers, reinforcements, colors and the like.
The particulate solid additive material may be any of a wide
variety of materials which impart special properties to the final
structure such as wear resistance, lubricity, electrical,
magnetic, temperature conductivity or isolation, and the like.
Some inexpensive particulate materials generally are readily
available at a particular job site. Natural mineral particulate
material such as sand and gravel normally are present or can be
produced simply by crushing rock at the site.
Waste or recycled materials which can be shredded or ground
into particles of suitable size can be utilized. Particularly
useful are particles formed by shredding or grinding discarded
tires and similar products. Since the particles are encapsulated
with the resin forming material and not saturated therewith, many
different waste materials may be employed.
The above description and the accompanying drawings show that
the present invention provides a novel multiaxis rotational
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molding method and apparatus which not only overcome the
deficiencies and shortcomings of earlier expedients, but in
addition provide novel features and advantages not found
previously. The method and apparatus of the invention provide
simple inexpensive means for producing uniform high quality
products efficiently and at high rates of production.
The apparatus of the invention is efficient in its design
and operation and is relatively inexpensive. Commercially
available materials and components can be utilized in the
fabrication of the apparatus using conventional metal working
techniques and procedures.
Structures can be produced automatically with the apparatus
of the invention by operators with limited experience and aptitude
after a short period of instruction. The apparatus is durable in
construction and has a long useful life with a minimum of
maintenance.
The method and apparatus of the invention can be utilized to
mold a wide variety of different products. Variations in
structure, configuration and composition of the products can be
achieved simply and quickly with the method and apparatus of the
invention.
It will be apparent that various modifications can be made
in the mul.tiaxis rotational molding method and apparatus described
in detail above and shown in the drawings within the scope of the
present invention. The size, configuration and arrangement of
components can be changed to meet specific requirements. For
example, the mold assemblies and mixing chambers may be arranged
differently with respect to one another. In addition, the number
and sequence of processing steps may be different. Also, the
apparatus may include other drive and actuating components and
mechanisms.
These and other changes can be made in the method and
apparatus described provided the functioning and operation thereof
are not adversely affected. Therefore, the scope of the present
invention is to be limited only by the following claims.
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