U.S. patent application number 10/492924 was filed with the patent office on 2004-11-04 for compression molding using a self aligning and activating mold system.
Invention is credited to Feguer, Thomas Ray, Neate, John Aubrey, Newman, Craig Alan.
Application Number | 20040217518 10/492924 |
Document ID | / |
Family ID | 25529616 |
Filed Date | 2004-11-04 |
United States Patent
Application |
20040217518 |
Kind Code |
A1 |
Newman, Craig Alan ; et
al. |
November 4, 2004 |
Compression molding using a self aligning and activating mold
system
Abstract
A compression molding system and method, including a mold set
and one or more hydraulic cylinders (42,44) that create a
self-aligning and self-activating operating unit. The hydraulic
cylinders can include a combination of activation and clamping
cylinders. The mold set includes a first and second mold section
(22,24) and a source of heat (87) is provided to heat the mold set.
The mold sections are constructed of individual plates or bar (16),
and machined to define a mold cavity (25). Reinforcement plates
(38,41) can be attached to the mold sections and add structure and
integrity to the system. A computer control system (56) interprets
data from the activation hydraulic cylinders and monitors and
controls hydraulic fluid flow into and out of each cylinder and a
power unit pumps hydraulic fluid into and out of the chambers
within the activation and clamping cylinders (42,44).
Inventors: |
Newman, Craig Alan; (East
Lansing, MI) ; Neate, John Aubrey; (Niles, MI)
; Feguer, Thomas Ray; (Grand Ledge, MI) |
Correspondence
Address: |
FOSTER, SWIFT, COLLINS & SMITH, P.C.
313 SOUTH WASHINGTON SQUARE
LANSING
MI
48933
US
|
Family ID: |
25529616 |
Appl. No.: |
10/492924 |
Filed: |
April 14, 2004 |
PCT Filed: |
October 11, 2002 |
PCT NO: |
PCT/US02/32590 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10492924 |
Apr 14, 2004 |
|
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|
09982902 |
Oct 18, 2001 |
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6510720 |
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Current U.S.
Class: |
264/319 ;
425/149; 425/407; 425/416 |
Current CPC
Class: |
B29K 2105/0854 20130101;
B29C 2043/5833 20130101; B29C 2045/564 20130101; B29C 45/1761
20130101; B21D 37/12 20130101; B30B 1/34 20130101; B29C 33/20
20130101; B29C 2043/5808 20130101; B29C 43/58 20130101; B29C 43/361
20130101; B21D 26/039 20130101; Y10T 29/49805 20150115; B29C
2043/5858 20130101 |
Class at
Publication: |
264/319 ;
425/149; 425/407; 425/416 |
International
Class: |
B29C 043/02 |
Claims
We claim:
1. An apparatus for compression molding a charge of material into a
work piece comprising: a mold set including a first mold section
and a second mold section; at least one activation cylinder mounted
to one of said first and second mold sections, said at least one
activation cylinder being adapted for extending and retracting a
first cylinder rod, said cylinder rod slidably extending through an
aperture in said one mold section and having an end attached to the
other of said first and second mold sections; and a source of heat
for the mold set.
2. The apparatus of claim 1 wherein said at least one activation
cylinder comprises a hydraulic cylinder having extension and
retraction chambers each connected to a controllable source of
pressurized hydraulic fluid.
3. The apparatus of claim 1, wherein said source of heat for said
mold set comprises steam.
4. The apparatus of claim 1, wherein said source of heat for the
mold set comprises hot oil.
5. The apparatus of claim 1, wherein said source of heat for the
mold set comprises resistance heat.
6. The apparatus of claim 1, further comprising at least one
clamping cylinder mounted to one of said first and second mold
sections, said at least one clamping cylinder being adapted for
extending and retracting a second cylinder rod having a second end
releasably mounted to the other of said first and second mold
sections.
7. The apparatus of claim 6 wherein said at least one clamping
cylinder comprises a hydraulic cylinder having extension and
retraction chambers each connected to a controllable source of
pressurized hydraulic fluid.
8. The apparatus of claim 1, further including a computer control
system connected to the compression molding apparatus to control
the mold process and insure that said first and second mold
sections remain substantially parallel to each other during
operation.
9. The apparatus of claim 8 further comprising linear transducers
encased in said activation cylinders, wherein said transducers
transmit continuous linear position data to said computer control
system, and wherein said computer control system interprets
incoming data from said at least one activation cylinder and
monitors and controls hydraulic fluid flow into and out of said
retraction and extension chambers.
10. The apparatus of claim 7 further comprising linear transducers
encased in the activation cylinders, wherein said transducers
transmit continuous linear position data to a computer control
system, and wherein said computer control system interprets
incoming data from said at least one activation cylinder and said
at least one clamping cylinder and monitors and controls hydraulic
fluid flow into and out of said retraction and extension
chambers.
11. The apparatus of claim 1, wherein said first and second mold
sections are comprised of a plurality of individual plates
connected together.
12. The apparatus of claim 1, wherein said first and second mold
sections are comprised of a plurality of solid steel bar-stock
pieces connected together.
13. The apparatus of claim 6, wherein said first and second mold
sections are comprised of a plurality of individual plates
connected together.
14. The apparatus of claim 6, wherein said first and second mold
sections are comprised of a plurality of bar-stock pieces connected
with together.
15. The apparatus of claim 1, wherein said first mold section and
second mold section in a closed position have an interior surface
that defines a mold cavity.
16. The apparatus of claim 1 further comprising support pillars
affixed to one of said first and second mold sections.
17. The apparatus of claim 1, wherein said at least one activation
cylinder is arranged on a periphery of said mold set.
18. The apparatus of claim 1, wherein said at least one activation
cylinder is positioned substantially in the center of said mold
set.
19. The apparatus of claim 6, wherein said at least one activation
cylinder and said at least one clamping cylinder are arranged on a
periphery of said mold set.
20. The apparatus of claim 19, wherein said at least one activation
cylinder and said at least one clamping cylinder are arranged in
opposing orientation to each other.
21. The apparatus of claim 19, wherein said at least one activation
cylinder and said at least one clamping cylinder are arranged in an
alternating layout.
22. The apparatus of claim 1, wherein one of said first and second
mold sections includes a plurality of stopping blocks.
23. The apparatus of claim 1, wherein the charge of material is
molded at a force of 75 to 350 psi.
24. The apparatus of claim 1, wherein said mold set includes
reinforcement plates attached along an exterior surface of said
mold set.
25. The apparatus of claim 6, wherein said mold set includes
reinforcement plates attached along an exterior surface of said
mold set.
26. A method of compression molding using an apparatus including a
mold set having first and second mold sections, means to heat the
mold set, at least one activation cylinder connected to one of the
first and second mold sections, the at least one activation
cylinder including a retraction chamber, an extension chamber and a
first cylinder rod having a first cylinder rod end attached to the
other of the first and second mold sections, and at least one
clamping cylinder connected to one of the mold sections, the at
least one clamping cylinder including a second retraction chamber,
a second extension chamber and a second cylinder rod having a
second cylinder rod end releasably mounted to the other of the mold
sections, the method comprising the steps of: heating the mold set;
placing a charge of material to be formed on one of the first and
second mold sections; moving one of the mold sections towards the
other mold section; actuating the second cylinder rod to meet the
one mold section and actuating a lock member to releasably hold the
second cylinder rod end to the one mold section; and pressing the
mold sections together at a predetermined pressure for a
predetermined time to mold the charge of material.
27. The method of claim 26, wherein the step of moving one of the
mold sections includes pumping fluid out of the extension chamber
and into the retraction chamber of the at least one activation
cylinder.
28. The method of claim 26, wherein the charge of material is
molded at a force of 75 to 350 psi.
29. The method of claim 26, further comprising the step of:
releasing the lock member thereby releasing the second cylinder rod
from said one mold section.
30. The method of claim 29 further comprising the step of: moving
the one mold section away from the other mold section.
31. The method of claim 30, wherein the step of moving the one mold
section away from the other mold section includes evacuating the
fluid from the retraction chamber of the activation cylinder and
pumping the fluid back into the extension chamber.
32. The method of claim 31 further comprising the step of: removing
the formed material.
33. The method of claim 32 further comprising the step of:
retracting the clamping cylinder rod thereby increasing
accessibility to the formed material.
34. A method of compression molding using an apparatus including a
mold set having first and second mold sections, a means to heat the
mold set, and at least one activation cylinder mounted to one of
the first and second mold sections, the activation cylinder
including a retraction chamber and an extension chamber and further
including a cylinder rod having a cylinder rod end mounted to the
other of the first and second mold sections, the method comprising
the steps of: heating the mold set; placing a charge of material to
be formed on the one of the mold sections; moving one mold section
towards the other mold section; pressing the mold sections together
at a predetermined pressure for a predetermined time to mold the
charge of material.
35. The method of claim 34, wherein the charge of material is
molded at a force of 75 to 350 psi.
36. The method of claim 34, wherein the step of moving the one mold
section towards the other mold section includes pumping fluid out
of the extension chamber and into the retraction chamber of the at
least one activation cylinder.
37. The method of claim 34 further comprising the step of: moving
the one mold section away from the other mold section.
38. The method of claim 37, wherein the step of moving the one mold
section away from the other mold section includes evacuating the
fluid from the retraction chamber of the at least one activation
cylinder and pumping the fluid back into the extension chamber.
39. The method of claim 38 further comprising the step of: removing
the formed material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part to U.S.
non-provisional application Ser. No. 09/982,902 entitled "Hydraulic
Pressure Forming Using a Self Aligning and Activating Die System,"
filed Oct. 18, 2001. The entire disclosure of U.S. application Ser.
No. 09/982,902 is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to compression
molding, and specifically to compression molding using a
self-aligning and activating mold system and method.
[0004] 2. Discussion of the Prior Art
[0005] Various molding processes exist to produce both simple and
complex shapes having a wide range of geometry and thickness. Two
existing processes are compression molding and resin transfer
molding.
[0006] Compression molding converts uncured (un-exposed to heat)
thermoset sheet molding compounds (SMC) known in the art into
various products by applying pressure in a closed mold that is
heated to cure (set) the SMC. SMC molding typically includes a
compression mold mounted into a hydraulic press of sufficient
tonnage to generate adequate internal force to cause the heated SMC
material to flow and fill the mold. In use, a charge (material to
be formed) of SMC is placed on a lower section of a mold set. The
press is closed under controlled conditions to bring the two mold
sections together resulting in compression molding of the SMC.
These systems typically require a molding pressure of between 750
psi (53 bar) to 1500 psi (103 bar) to adequately flow the compound
and fill the mold cavity. The molds are typically heated to around
290.degree. F. to 310.degree. F. to complete the cure (set) of the
thermoset resin used in the SMC material. The mold/press remains
closed and under pressure during the cure cycle. The duration of
the cure cycle is determined by part thickness. A typical cure time
for a 0.125 inch thick part would be between 60 and 90 seconds.
[0007] Currently, a high tonnage compression press is required to
generate the molding pressures necessary to form a standard SMC
part. These presses require special installation and deep
foundations of reinforced concrete and can weigh many tons and can
be over twenty (20) feet in height. Because of their large size and
weight, the presses are usually assembled in one facility,
disassembled, and then shipped in sections and re-assembled
on-site. This increases overall costs and start-up times.
[0008] Thus, conventional SMC presses are expensive and therefore
require a long-term investment. Molds (tools) used in a
conventional SMC compression process are similarly expensive due to
the required structural integrity necessary to handle the high
molding pressures. The molds are typically machined from at least
two rectangular solid steel billets. These billets are engineered
to withstand the high pressures of compression molding. Billet
machining can remove as much as fifty percent of the original
material, thus adding to the overall cost of the mold design.
Because of the size and expense of SMC compression molding
operations, SMC part production is usually restricted to high
volume parts (e.g., more than 50,000 units annually). Mid and low
volume product runs are often prohibitively expensive to produce
using this technology.
[0009] A second conventional molding process is resin transfer
molding (RTM). RTM injects a liquid thermoset resin into a heated
or unheated mold cavity containing a dry glass preform (such as
sheets of woven glass material or fiberglass) and allowed to
solidify (or cure) into a desired part shape. RTM is common and
widely used in industry.
[0010] In use, RTM systems typically have upper and lower mold
halves. These halves are usually separated using a chain hoist.
Once open, the dry glass preform is placed into the mold cavity.
The mold halves are then placed back together and the preform is
sealed within the mold halves. The resin is injected into the mold
cavity, impregnating the preform. The pressure needed to complete
the injection is typically 50 psi (3.5 bar). The resin can then
cure at either room temperature or a predetermined elevated
temperature depending on the desired rate of cure. Once the mixture
has solidified, the mold is opened and the part is removed.
[0011] Resin transfer molds typically have a thin nickel tool
surface backed by epoxy. The structural elements that support the
tool surface can include a combination of plywood, fiberglass and
steel. RTM tools are constructed at relatively low cost when
compared to SMC compression molds since little structural integrity
is needed to handle its relatively low molding pressures (50 psi
compared to 1000 psi in SMC systems). In addition, the RTM process
uses no press and has limited infrastructure costs.
[0012] Though relatively inexpensive, RTM has many limitations that
make the process undesirable. These include a frequent inability to
make a final shape part; a relatively long cycle time; multi-phase
operations are often required; very operator skill dependent; part
geometry limitations; limited ability to achieve class A surface
finish (i.e. visible or show surface); and part-to-part
inconsistency. Given the above limitations, RTM is mainly used for
very low production volumes, non-class A surface parts, and simple
shapes.
[0013] It would be advantageous to overcome the limitations of the
RTM systems without the expense and structural requirements of the
conventional SMC systems. New SMC compounds have recently been
developed that mold at much lower pressures (e.g., between 75 psi
to 350 psi). These are now products known in industry as low
pressure molding compounds (LPMC) and low pressure sheet molding
compounds (LPSMC) which are sold respectively under the trademarks
CRYSTIC IMPREG made by Scott Bader Company Ltd of Northamptonshire,
England and SMC-LITE made by Ashland Specialty Chemical Company
(Composite Polymers Division) of Columbus, Ohio. Such compounds
include glass fiber composite impregnated with polyester resins or
low viscosity resins including isophthalic and orthosphthalic
resins and the like. A new system and method, combining the
simplicity and cost effectiveness of an RTM system with the part
consistency and class A finish capability of the SMC compression
mold process is now possible for molding the new LPMC and LPSMC
materials.
SUMMARY OF THE INVENTION
[0014] Accordingly, the present invention provides a compression
molding apparatus and method using a self-aligning and activating
mold (SAAM) system. The present invention uses fabricated steel
molds to mold the new low pressure molding compounds (LPMC) and low
pressure sheet molding compounds (LPSMC). Using a fabricated mold
set integrated to a series of hydraulic cylinders to create a
self-contained operating unit, the system eliminates the need for a
solid steel tool/mold set operated by a conventional high tonnage
hydraulic press.
[0015] In one embodiment of the present invention an apparatus for
compression molding includes a mold set having first and second
mold sections and a source of heat for the mold set. At least one
activation cylinder is mounted to either the first mold section or
the second mold section and has a retraction chamber and an
extension chamber. The activation cylinder further includes a
cylinder rod having an end mounted to the other of the first and
second mold sections.
[0016] In another embodiment of the present invention a method of
compression molding is provided using an apparatus that includes a
mold set having first and second mold sections and a source of heat
for the mold set. At least one activation cylinder is mounted to
one of the first and second mold sections. The activation cylinder
includes a retraction chamber and an extension chamber, and further
includes a first cylinder rod having an end mounted to the other of
the first and second mold sections. At least one clamping cylinder
is mounted to one of the first and second mold sections. The
clamping cylinder includes a second retraction chamber, a second
extension chamber, and a second cylinder rod having a second end
releasably mounted to the other of the first and second mold
sections. The method includes heating the mold set; placing a
charge of material to be formed on one of the first and second mold
sections; moving one of the mold sections towards the other mold
section; actuating the second cylinder rod to meet the one mold
section and actuating a lock member to releasably hold the second
cylinder rod end to the one mold section; and pressing the mold
sections together at a predetermined pressure for a predetermined
time to mold the charge of material.
[0017] In another embodiment of the present invention a method of
compression molding is provided using an apparatus including a mold
set having a first and second mold section, and a source of heat
for the mold set. At least one activation cylinder is connected to
one of the mold sections. The activation cylinder includes a
retraction chamber, an extension chamber, and further includes a
cylinder rod having a cylinder rod end mounted to the other of the
mold sections. The method comprises the steps of heating the mold
set; placing a charge of material to be formed on one of the mold
sections; moving one mold section towards the other mold section;
and pressing the mold sections together at a predetermined pressure
for a predetermined time to mold the charge of material.
[0018] While most mold sets of this invention are oriented so as to
use upper and lower sections to benefit from the force of gravity
in insertion of moldable material in the lower mold section, it
will be understood that the invention is equally applicable to
configurations wherein the sections are positioned in a
side-by-side orientation (See FIG. 13). Thus, it should be
understood that the invention contemplates the use of first and
second mold sections irrespective of their orientation, and that
the use of the terms "upper" and "lower" herein is for illustrative
purposes and for ease of understanding, only, and should not be
deemed to limit the scope of the invention to any particular
orientation of the mold sections.
[0019] Other advantages and features of the present invention will
become more apparent to persons having ordinary skill in the art to
which the present invention pertains from the following description
taken in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE FIGURES
[0020] The foregoing advantages and features, as well as other
advantages and features will become apparent with reference to the
description and figures below, in which like numerals represent
like elements and in which:
[0021] FIG. 1 is a perspective view of a compression molding system
of the present invention;
[0022] FIG. 2 is a side view of a fabricated mold set of the
present invention before the mold cavity is machined;
[0023] FIG. 3 is a side view of a fabricated mold set of the
present invention machined to a desired work piece shape;
[0024] FIG. 4 is a side view of a fabricated mold set of the
present invention including reinforcement plates;
[0025] FIG. 5 is a side view of the compression molding system of
the present invention including a clamping hydraulic cylinder and
an activation hydraulic cylinder;
[0026] FIG. 6 is a compression mold system of the present invention
in an open position;
[0027] FIG. 7 is an alternate embodiment of the present invention
using four activation cylinders;
[0028] FIG. 8A is a plan view of the alternate embodiment in FIG.
7;
[0029] FIG. 8B is a sectional view cut through line 8B-8B in FIG.
8A;
[0030] FIG. 9 illustrates steps of a compression mold system of the
present invention in an open position loading a charge, a closed
position molding the charge, and in an open position removing the
molded charge;
[0031] FIG. 10 illustrates an alternate embodiment of the present
invention having one activation cylinder;
[0032] FIGS. 11A & 11B illustrate a top view of FIG. 10 and a
sectional view cut through line 11B-11B in FIG. 11A
respectively;
[0033] FIG. 12 illustrates an alternate embodiment of the present
invention including four activation cylinders and two clamping
cylinders.
[0034] FIG. 13 illustrates of the present invention mounted on a
truck having activation and clamping cylinders.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The present invention relates to a compression molding
system that combines the advantages of the conventional sheet
molding compound (SMC) systems with the resin transfer molding
systems (RTM) while eliminating known disadvantages of each of
these systems. The present invention replaces both the large solid
steel mold set mounted to a conventional high tonnage hydraulic SMC
press and instead uses a fabricated or bar-stock mold set
integrated to a series of strategically placed hydraulic cylinders
and optional reinforcement plates.
[0036] Generally, the present invention is a self-contained,
self-aligning and self-activating molding (SAAM) system 20 capable
of developing the pressure required for compression molding of new
low pressure molding compounds (LPMC) and other similar materials
that have low pressure molding and curing capabilities. The new
LPMC material changes state (such as to a liquid) when heated
thereby requiring less pressure to mold a shaped part. The present
invention achieves the desired molding capabilities in a smaller,
lighter and less expensive package compared to conventional SMC
molding systems. It is also an improvement over the RTM system in
that the limitations of the RTM system as outlined previously, are
eliminated.
[0037] The present invention can be operated on a typical six-inch
reinforced concrete factory floor, eliminating the need for a
larger concrete pad as required by conventional SMC molding
systems. The working height of the new SAAM molding system 20 can
be designed to suit the operators by altering the location of the
activation cylinders and defining the desired height of the support
pillars. The system 20 can be assembled, tested, demonstrated and
approved in one facility and shipped assembled to the manufacturing
plant as a "turn-key" operation. Thus, the system provides a cost
advantage through reduced capital cost, and a faster time for set
up and production.
[0038] The major components of the molding system 20 of the present
invention are the mold set, hydraulic cylinders, hydraulic power
unit, and system controller. FIG. 1 illustrates an embodiment of
the present invention utilizing a plurality of mold sets and
cylinders connected together. Alternate embodiments of the present
invention demonstrate variations in the types of application
available by varying the number and configuration of the types of
hydraulic cylinders, the mold set shape and the orientation of the
molding apparatus. The apparatus of the present invention can be
oriented horizontally or vertically depending on the particular
application.
[0039] FIG. 2 illustrates the mold sections of a mold set before
the mold sections have been machined. The mold sections can include
a plurality of individual plates or a plurality of solid steel
bar-stock 16, connected together in various shapes and sizes to
form a mold set the shape and size of a desired part. The plates
(or bar-stock) 16 can be made of steel or any other material
capable of supporting the forces generated during the molding
process for a given application. The plates (or bar-stock) 16 may
be pre-formed to the approximate part shape by methods such as
bending, rolling, flame/gas cutting, and forging. The plates (or
bar-stock) 16 may be connected together along their perimeter using
conventional means such as welding, as shown by weld points 26, or
bolting (not shown). Once connected, the plates 16 form a lower
mold section 22 and an upper mold section 24. The mold sections 22
and 24 are then machined to create a desired mold cavity 25
corresponding to the part to be molded (FIG. 5). Conventional
methods such as milling or computer numerically controlled (CNC)
machining can be used to machine the mold sections. This mold set
replaces the need to machine the mold from a single steel
billet.
[0040] Most mold sets of this invention are oriented to use a lower
mold section and an upper mold section to benefit from the force of
gravity in insertion of moldable material in the lower mold
section. It will be understood that the invention is equally
applicable to configurations wherein the mold sections are
positioned in a side-by-side orientation (See FIG. 13). Thus, it
should be understood that the invention contemplates the use of
first and second mold sections irrespective of their orientation,
and that the use of the terms "upper" and "lower" herein is for
illustrative purposes and for ease of understanding, only, and
should not be deemed to limit the scope of the invention to any
particular orientation of the mold sections.
[0041] The mold sections 22 and 24 can also include a heat cavity
43 configured to receive a heating element, which may be, for
example, a resistance heater, or, preferably a heated fluid medium
such as hot oil or steam (FIG. 2). A conventional pumping system 86
can be used to heat and pump steam or oil into and out of the heat
cavities 43 (FIG. 1). The particular heat cavity 43 shown in the
figures is representative of the type of cavity required for use of
steam as a heating medium. If hot oil is being used, a smaller
cavity design will suffice. The heating medium is pumped into the
heat cavities 43 through heat ports 45 and heats the mold sections
22 and 24 to the required temperature needed to mold a particular
work piece (FIGS. 11A & B).
[0042] The molding system 20 can be supported by a plurality of
support pillars 14 to place the molding system 20 at a height
convenient for a typical worker. The support pillars 14 can be
affixed on one end to the lower mold section 22 using conventional
methods such as bolting or welding. The opposite end of the support
pillars 14 can be mounted to the floor using conventional methods
such as lag bolts. The support pillars 14 support the weight of the
system 20 and securely fasten the system 20 to the floor to prevent
it from moving and reduce excessive vibration during operation.
FIGS. 1 and 7 show two different types of support pillars 14, but
any number of other possible support pillar configurations could
also be used.
[0043] FIG. 3 illustrates the machined mold surfaces 32 and 33 of
mold sections 22 and 24. The machined mold surfaces 32 and 33
represent the shape of the part to be molded and define the mold
cavity 25. Surfaces 32 and 33 can also be surface finished by
conventional means known in the art (e.g., repairing, detailing,
grinding, sanding, and polishing) to create an acceptable
production surface finish. Mating perimeter surfaces 34 and 35 of
the upper and lower mold sections serve to define the periphery of
mold cavity 25 and are oriented parallel to each other.
[0044] FIG. 4 illustrates the mold sections 22 and 24 including
reinforcement plates 36, activation hydraulic cylinder mounting
plate 38, clamping hydraulic cylinder mounting plate 39, activation
hydraulic cylinder rod end mounting plate 40, and clamping
hydraulic cylinder rod end mounting plate 41, all of which are
mounted to the mold sections 22 and 24 using conventional means
such as welding or bolting. The illustrated embodiment shown in
FIG. 1 is shown with six sets of reinforcement plates 36 (a first
set on each upper mold section 24 and a second set on each lower
mold section 22). The reinforcement plates 36 provide strength and
stability to the molding system 20 and can vary in quantity, shape,
size and location depending on the size and particular embodiment
of the molding apparatus. Stopping blocks 37 can be mounted to
either the perimeter surface 34 of lower mold section 22 or
perimeter surface 35 of upper mold section 24 and are used to set
the gap between the upper and lower mold sections 22 and 24 by
stopping the mold surfaces 32 and 33 from contacting each other.
The thickness of the part to be molded may be dictated by the size
of the stopping blocks 37. The stopping blocks 37 can be various
shapes and sizes depending on the particular mold system design and
for the particular part to be molded.
[0045] FIG. 5 illustrates an embodiment of the present invention
where the mold sections 22 and 24 are connected to an activation
hydraulic cylinder 42 and a clamping hydraulic cylinder 44. The
activation cylinder 42 can raise and lower the upper mold section
24 to allow convenient removal of a work piece. The clamping
cylinder 44 allows for additional reinforcement to maintain the
mold set in a closed position during operation.
[0046] The activation hydraulic cylinder 42 is mounted to the
activation hydraulic cylinder mounting plate 38 on the lower mold
section 22 and the clamping hydraulic cylinder 44 is mounted to the
clamping hydraulic cylinder mounting plate 39 on the lower mold
section 22. The activation hydraulic cylinder 42 has a first
cylinder rod 46 attached to a first piston 60. First cylinder rod
46 has a first cylinder rod end 48 that is fixedly mounted to the
activation hydraulic cylinder rod end mounting plate 40 on the
upper mold section 24 and extends slidably through a closely
fitting aperture in plate 38. The activation hydraulic cylinder 42
includes two chambers defined as a first retraction chamber 62 and
a first extension chamber 64. Chambers 62 and 64 can have one or
more fluid entry and exit points 80. Fluid is pumped to and from
the first retraction and extension chambers 62 and 64 to provide
the clamping and extension force needed to move upper mold section
24 to and from lower mold section 22 using a conventional pumping
system 86 and computer control system 56 (such as a Position Linear
Control (PLC) illustrated in FIG. 1).
[0047] The clamping hydraulic cylinder 44 has a second cylinder rod
50 attached to a second piston 66. The second cylinder rod 50 has a
second cylinder rod end 52 that extends into and through the
clamping hydraulic cylinder rod end mounting plate 41 and is
configured to releasably lock into position into a rod end slide
coupler unit 54. In the preferred embodiment, the clamping
hydraulic cylinder rod end mounting plate 41 includes the rod end
slide coupler unit 54, which is configured to receive the second
cylinder rod end 52. FIG. 5 illustrates the rod end slide coupler
unit 54 in its closed position locking the second cylinder rod end
52 securely in position. The rod end slide coupler unit 54 engages
when the upper mold section 24 reaches a predetermined pause
position. Preferably, the predetermined pause position is when the
upper mold section 24 is within approximately 25-50 mm of the lower
mold section 22.
[0048] The clamping hydraulic cylinder 44 has two chambers defined
as a second retraction chamber 68 and a second extension chamber
70. Each chamber 68 and 70 can have one or more second fluid entry
and exit points 82. Fluid can be pumped to and from the second
retraction and second extension chambers 68 and 70 using the
pumping system 86 and PLC control system 56. The clamping hydraulic
cylinder 44 assists in providing the clamping and extension forces
needed to hold the upper and lower mold sections 22 and 24 together
during the molding process.
[0049] FIG. 6 illustrates the embodiment shown in FIG. 5 in an open
position with the rod end slide coupler unit 54 shown in its open
position. When the mold sections 22 and 24 are in an open position,
a part loading and removal zone 58 is created. With the rod end
slide coupler unit 54 in its open position, the second cylinder rod
end 52 can be removed from the clamping hydraulic cylinder rod end
mounting plate 41, and the first cylinder rod 46 can be extended to
raise the upper mold section 24. When upper mold section 24 is
closing towards lower mold section 22, the first cylinder rod 46
and second cylinder rod 50 provide sufficient forming/closing
pressure to mold the part within the mold cavity 25. Pressure
typically remains constant during the complete curing stage.
[0050] In the illustrated embodiment shown in FIGS. 5 & 6, the
clamping hydraulic cylinder 44 assists the activation hydraulic
cylinder 42 in holding the mold sections 22 and 24 in a closed
position during operation. The activation hydraulic cylinder 42 in
combination with the clamping hydraulic cylinder 44 generate the
clamping force required to keep mold sections 22 and 24 together
and under pressure during the molding and curing stages. Only the
activation hydraulic cylinder 42 controls the movement of mold
section 24 away from mold section 22 to allow for part removal.
[0051] In summary, the clamping hydraulic cylinders 44 differ from
activation hydraulic cylinders 42 in four ways. First, as stated
above, the clamping hydraulic cylinders 44 provide clamping force
only to hold the mold sections 22 and 24 together during the
molding stage. The clamping hydraulic cylinders 44 do not aid in
raising and lowering the upper mold section 24. Second, the
clamping hydraulic cylinders 44 have a unique latching mechanism
(the rod end slide coupler unit 54). By comparison, the activation
hydraulic cylinders 42 have a fixed attachment on the first
cylinder rod ends 48. Third, the clamping hydraulic cylinders 44
allow unfettered ingress and egress of the charge/part because the
second cylinder rod 50 does not reach into the charge/part
loading/unloading zone 58 and can be retracted out of the way.
Finally, the clamping hydraulic cylinders 44 are more economical,
since second cylinder rod 50 has a shorter stroke.
[0052] In an alternate embodiment (FIGS. 7 & 8), a system 20'
using the present invention includes only four activation hydraulic
cylinders 42 and no clamping hydraulic cylinders 44. The activation
hydraulic cylinders 42 can open the mold sections 22' and 24' to
allow insertion and removal of the molded parts and provide the
required pressure for molding of a part. In this embodiment, the
system 20' is inverted in that the activation hydraulic cylinders
42 are attached to a top side of the upper mold section 24'. The
activation cylinder rod end 48 is fixedly attached to the lower
mold section 22' instead of the upper mold section 24'. As the
upper mold section 24 moves away from the lower mold section 22'
during operation, the activation cylinders 42 move with the upper
mold section 24'. Reinforcement plates 36' are included in this
embodiment and are positioned on the sides and exterior of the mold
sections 22' and 24'. These optional reinforcement plates 36' add
strength and stability of the system in configurations where higher
pressures are indicated.
[0053] In another embodiment, the system 20" includes only one
activation hydraulic cylinder 42 and no clamping hydraulic
cylinders 44 (FIGS. 10-11). In this embodiment, the cylinder 42 is
positioned centrally to distribute the load equally and insure that
the perimeter surfaces 34" and 35" of upper and lower mold sections
22" and 24" remain parallel during operation. This embodiment is
similarly inverted with the activation cylinder 42 being attached
to the topside of the upper mold section 24". This type of single
activation system would be used for compression molding of smaller
components that require less pressure. The smaller size of the
system would also eliminate the need for reinforcement plates 36
used in the previous embodiments.
[0054] FIG. 12 illustrates another embodiment of the molding system
20'" of the present invention. This configuration illustrates four
activation cylinders 42 and two clamping cylinders 44. FIG. 13
illustrates a mobile embodiment 20"" of the present invention where
the molding system is mounted to a truck to provide for the ability
to locate the molding process at a desired remote location. In this
embodiment the molding system is oriented horizontally and is
mounted to the truck on tracks to allow the mold sections to slide
along the tracks as they move together and apart during operation.
This embodiment illustrates a compression molding system of the
present invention having one activation cylinder 42 and one
clamping cylinder 44.
[0055] The activation hydraulic cylinders 42 and clamping hydraulic
cylinders 44 of the present invention are typically arranged on the
periphery of the mold tool set except as illustrated in FIGS. 10
and 11. In the illustrated embodiments of FIGS. 1, 7 & 12, the
activation hydraulic cylinders 42 and the clamping hydraulic
cylinders 44 are placed symmetrically around the mold set. The
activation hydraulic cylinders 42 and clamping hydraulic cylinders
44 can be placed in a wide range of alternative layouts to suit the
specific molding conditions and parameters as well as sound
engineering requirements. The activation hydraulic cylinders 42 and
clamping hydraulic cylinders 44 can be placed in an alternating
layout or the cylinders 42 and 44 can be in an opposing layout
where all the activation cylinders 42 are one side and the clamping
cylinders 44 are on the opposite side of the particular system. The
key to configuring cylinder 42 and 44 placement is to maintain an
equal distribution to limit vertical and side mold deflection
caused by pressure during production, and keep the upper mold
section 24 parallel to the lower mold section 22.
[0056] The movement of each activation hydraulic cylinder 42 can be
monitored by linear transducers (not shown), which are encased in
the body of each activation hydraulic cylinder 42. The transducers
transmit continuous linear position data to the computer control
system (PLC) 56 in FIG. 1. The PLC 56 interprets incoming data from
all the activation hydraulic cylinders 42 in a given system. The
PLC 56 also monitors and controls hydraulic fluid flow into and out
of each activation hydraulic cylinder 42 and clamping hydraulic
cylinder 44 via valves at each cylinder's fluid entry and exit
points 80 and 82. The PLC 56 can also control the operation of the
clamping hydraulic cylinders 44 when they are included in the
system. The PLC 56 insures uniform speed, position, and
self-alignment of the first cylinder rods 46 so that the upper and
lower mold sections 22 and 24 always remain parallel and aligned
with each other.
[0057] The molding system 20 of the present invention is designed
to meet the individual needs of a specific part to be molded.
Therefore, the forces acting on the mold sections 22 and 24 must be
calculated for a specific configuration. First, the surface area of
the part is calculated. Next, the maximum pressure required to mold
the part is determined. The product of surface area and maximum
required molding pressure determines the tonnage required for the
particular molding system (surface area.times.required molding
pressure=tonnage). Required molding pressure can vary from part to
part depending on the complexity and geometry of the part, the
depth of draw and desired finish. Steeper and deeper draw parts
with thin wall thickness will require higher molding pressures. The
typical pressures for the present invention range between 70 psi (5
bar) and 50 psi (11 bar) when using LPMC, but may increase to 350
psi (27 bar) for LPSMC products.
[0058] Hydraulic cylinders must also be evaluated to determine
their output force. Output force is a function of the effective
area of the cylinders. The cylinder's effective area is calculated
using the formula for piston area (cylinder bore) minus the rod
diameter area (effective area=piston area-rod diameter). The total
output force of the activation hydraulic cylinders 42 and clamping
hydraulic cylinders 44 is specified to exceed the molding
force.
[0059] The method of using the molding system 20 of the present
invention utilizing an activation hydraulic cylinder 42 in
combination with a clamping hydraulic cylinder 44 as shown in FIGS.
1, 5 & 6, will now be described. Alternative methods can be
employed depending on the particular embodiment (described above)
to be used. The compression molding process begins with the mold
sections 22 and 24 in the open position and heated to approximately
300 degrees Fahrenheit. The heating process is achieved by
injecting hot oil or steam through ports 45 and into heat cavities
43 positioned just below the mold surfaces 32 and 33 (FIGS. 8B
& 11B). A pre-weighed charge (usually a sheet of material) of a
low-pressure molding compound (LPMC) is placed in position on the
lower mold section 22. The PLC 56 commands the molding sequence to
initiate. Fluid is pumped out of the first extension chamber 64 and
into the first retraction chamber 62 causing the mold sections 22
and 24 to close.
[0060] When the upper mold section 24 reaches the predetermined
pause position, (approximately 25 to 50 mm depending on the charge
and molding parameters) from the lower mold section 22, the
clamping hydraulic cylinder 44, second cylinder rod end 52 and
slide coupler unit 54 are engaged to assist the activation
hydraulic cylinder 42 in holding the upper and lower mold sections
22 and 24 together.
[0061] At the same time, the closing speed of the cylinders 42 and
44 is slowed to the required forming speed. Forming speed is
determined by trial and error and differs based on part geometry
and LPMC formulation.
[0062] The upper mold section 24 continues to move towards the
lower mold section 22 until the mold cavity 25 is closed. This
means that either the upper mold section 24 has closed onto the
lower mold section 22 with stopping blocks 37 (if used), or the
upper mold section 24 has closed against the LPMC material trapped
in the mold cavity between the upper and lower mold sections. Once
the mold is closed, the "cure time" duration is started.
[0063] The cure time is dependent on the thickness of the part
being molded--usually between 60 to 90 seconds per 0.125" (3 mm) of
thickness. Following the cure cycle completion, a command to open
the mold set will be issued by the PLC 56.
[0064] Fluid is evacuated from retraction chambers 62 and 68 of the
activation hydraulic cylinders 42 and clamping hydraulic cylinders
44 while simultaneously being pumped into the extension chambers 64
and 70. The transfer of fluid causes the upper mold section 24 to
separate from the lower mold section 22 to a pause position (the
same pause position as for the closing phase). At this position,
the rod end slide coupler unit 54 is disengaged, the activation
hydraulic cylinder 42 extends, lifting the upper mold section 24 to
a position that allows removal of the molded part. Simultaneous
with the activation hydraulic cylinder 42 being extended to open
the mold sections 22 and 24, the clamping cylinder rod 50 can be
retracted to increase accessibility if required. FIG. 9 illustrates
the process showing the mold set in an open/ready position, a
closed molding position and a part removal position respectively.
In an embodiment that does not include a clamping hydraulic
cylinder 44, the steps in the above method would apply excluding
the steps related to the clamping hydraulic cylinder 44.
[0065] The above-described embodiments of the present invention are
provided purely for purposes of illustration. Many other
variations, modifications, and applications of the invention may be
made.
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