Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to injection molding wherein
multiple cavities are simultaneously filled with plastic
material. The invention is particularly concerned with
situations where it is desired to mold a number of parts of
dissimilar size in the same moldt or to use several nozzles
for a single cavity, and also to adjust the mold gate opening
at each shut-off bushing to create optirnum flow conditions~
This is a division of copending Canadian Patent
Application Serial No. 335,543, filed September 13, 1979.
It is known to provide individual gate control on
molding machines themselves, as contrasted with mold shut-off
bushings. However, this means that the mold has to be
constructed to fit the particular molding machine, greatly
reducing the versatility of the construction and increasing
manufacturing costs where a number of different molded parts
! are to be made.
Kelly U.S. Patent No. 2,770,011 shows an injection
molding machine in which a timer controls a fluid motor
which operates retractable wedges so that gate pins for a
plurality of mold cavities may be simultaneously retracted.
However, there is no suggestion in Kelly of individual timing
and control of gate pins nor of positive retraction thereof
independently of material pressure. In Kelly, furthermore,
the gate pins are not adjustable and the material outlets to
the cavities are therefore of fixed size. The Kelly
construction therefore does not permit individual variation
of individual flow conditions to each cavity and it would not be
feasible to use this construction for the simultaneous
filling of cavities of dissimilar sizes.
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Natkins U.S. Patent No. 3,491,408 shows a
distribution manifold carrying a number of spring-urged valve
members which are retracted by material pressure, the extent
of opening of the valve members being individually adjustable.
Aside from the fact that this stop mechanism is shown on an
injection molding machine rather than on the mold itself,
it suffers from the drawback that injection pressure is used
to activate the gates. This often causes material to "explode"
into the cavity, inducing extra shear and creating additional
heat that may affect the plastic.
Bielfeldt et al. U.S. Patent No. 3,847,525 shows
an injection molding apparatus utilizing a distributing valve
for sequential delivery to individual mold cavities, with
rams controlled by double-acting pistons. This patent however
has numerous drawbacks as compared with the present invention
I which will become apparent from the following description.
Barrie U.S. Patent No. 3,909,169 and British Patent
No. 1,056,361 show injection molding systems having general
pertinency to the present invention. Strauss U.S. Patent No.
2,828,507 and Angell U.S. Patent No. 3,436,446 show gate pins
controlled by double acting fluid motors. These patents
however are not believed to teach the present invention.
It is an object of the present invention to provide
an improved apparatus for injection molding machines which
offers extreme flexibility in manufacturing, both as to
individual flow control of multiple cavities which are being
simultaneously filled, and also with respect to filling
dissimilar sizes of cavities at the same time, or the same
cavity with several nozzles.
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The present invention resides in a multi-cavity
mold die assembly for use with a plastic injection molding
machine having a machine nozzle. The assembly has a plurality
of gate pins and a plurality of fluid motor actuators with
means connecting each gate pin respectively to an advanceable
and retractable piston of one of the actuators. Means forms
access openings in-line with the gate pins and means is
provided for permitting removal of the gate pins through the
access opening.
In a specific embodiment of the invention a top
mounting plate is provided, for example by a oil manifold, and
the fluid motors are carried by the mounting plate. The access
openings are provided in the mounting plate in line with the
gate pins. The fluid motors may also have access openings in
line with the access openings of the mounting plate so that the
gate pins can be removed through the access openings in the
fluid motors and mounting plate.
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BRIFF DESCRIPTIO:~ OF THE DRAl~'I!`lrlS
_, .. . . . _ ...
Figure 1 is a cross-sectional view in elevation showing a
multiple cavity mold incorpora~ing th~ fea~ures of this inven-
~ion, the view showing one ~ate ~in in its open position and one
in its closed position to illustrate the operation.
Figure 2 is an enlaTged fragmentary cross-sectional view
showing the construction of a dual action fluid motor for a gate
pin.
Figure 3 is a view taken along the line 3-3 of Figure 2 and
showing the fluid passages for the motor.
~ igure 4 is a circuit diagTam showing the control means for
the system; and
Figure 5 is a schematic diagram of a modified form of the
invention in which cycle counters are provided for individual con-
trol of the cavities.
DESCRIPTION OF THE PREFERRED E~ODIME~T
_ _
A mold is generally indicated at 11 in Figure 1, having a
core ~art 12 and a cavity part 13. Mold 11 may have for example
four mold cavities of which two are partially shown in Figure 1
and indicated at 14 and 15. These parts may be dissimilar from
each other if desired and have different ~olumes.
A cavity back-up plate 16 is provided for cavity mold half
13, and a pair of shut-off bushings generally indicated at 17 and
18 are mounted in plate 16 and mold half 13. The shu~-off bushings
open on cavi~ies 14 and 15 respectively, a portion of the bushings
remote from the cavities being disposed between plate 16 and a ma-
nifold 19 and aligned with manifold passages 21 and 22. Spacer
means 23 is disposed between plate 16 and manifold 19. The mani-
fold has a single entry 24 which receives a machine nozzle shown
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partially in dot-dash lines at 25, A passage 26 leading
from entry 24 conducts material to branch passages 27 and 28
leading to passages 21 and 22 respectively.
Each bushing 17 and 18 comprises an outer housing
29 which surrounds the shank 31, a heater 32 being disposed
between these two parts~ A central material passage 33
extends through shank 31, the forward end 34 being tapered
and leading to an outlet orifice 35. The forward surface 36
of shank 31 is flush with the cavity. Passage 33 is connected
with passage 21 or 22 of the manifold.
A gate pin 37 is disposed within passage 33, the
forward end 38 of this pin being tapered so that in its
closed position, as seen with respect to bushing 18, the outlet
is closed. Pin 37 extends through passage 21 or 22 and
through a seal 39 in the manifold to a double-acting fluid
! motor generally indicated at 41 and shown in detail in Figures
2 and 3.
Each fluid motor 41 comprises a two-part housing 42
held together by bolts 43 and secured to the underside of
an oil manifold 44 by bolts 45 the oil manifold 44 forming a
top mounting plate for the fluid motors 41. The oil manifold
has a plurality of passages 46 and 47 connected to hoses 48
and 49 respectively. Passage 46 leads to an advancing chamber
51 while passage 47 is connected to a retracting chamber 52
within the cylinder. A piston 53 is slidably mounted in the
cylinder and has a double-ended piston rod 54,55. Piston rod
portion 54 is slidable in a bearing 56 while portion 55 slides
within a bearing 57.
A central passage 58 is formed in the piston and
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piston rod and is threaded at its rearward end 59. Gate pin
37 is disposed within passage 58 and its rearward end hO is
threadably mounted in portion 59 of the passage. Portion 60
is headed and has a slot 61 for screwdriver access. Pin 37
may thus be adjusted lengthwise by rotating head 60.
The rearward movement of piston 53 and therefore
of pin 37 is limited by a shoulder 62 at the end of chamber 51.
Depending on the adjustment of pin 37, the gap 63 (Figure 1)
which exists leading to orifice 35 when the pin is retracted
may be controlled. Variation in this opening may be desired
by individual molders or in accordance with other molding
conditions. An access hole 64 is provided in manifold 44 so
that pin 37 may be adjusted or removed for replacement, thls
access hole also providing clearance for piston rod portion 54.
Because of the fact that gate pin 37 is not in
I engagement with piston rod 55 except at its extreme rearward
end, heat transfer from the molten material to motor 41 will
be minimized. Moreover~ the gap between the gate pin and piston
rod will accommodate lateral shifting which could take place
as a result of heat expansion of manifold 19 during operation.
The construction and end mounting of motors 41 on manifold 44
means that all hoses 48 and 49 may be connected to the manifold
rather than directly to the motors. This reduces crowding
around the motors and permits them to be mounted close together
if necessary.
The above-described feature of providing the radial
clearances around the pins is also disclosed and is claimed
in the above-identified parent application 335,543.
Figure 4 is a circuit diagram showing the means for
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lndividually controlling opening and closing of the shut-off
pins. A limit switch 65 is provided which is closed in response
to closing of the mold halves 12 and 13. One contact 66 of
this switch is connected to one side 67 of a source of power
68. Foux switches, numbered 1, 2, 3 and 4 are provided, these
switches each having three positions, "auto", "off" and "open".
When in their "auto" position the contacts of the four switches
will be on the left hand side. Each switch is connected to a
solenoid-operated valve 69 for controlling fluid flow to and
from a particular bushing 17 or 18. The connection is through
a timer 71. Indicator lights 72 for showing the automatic
condition and further indicator lights indicated generally
at 73 for showing the valve conditions are also illustrated
but will not be described in detail.
In operation, assuming an initial condition in which
switches 1 to 4 are in "auto" position and mold halves 12
and 13 are separated, limit switch 65 will be open. Closure
of the mold halves will cause this switch to close, and power
will flow through conduits 74 to timer 71, closing the timer
switch 75. Current will flow through conduits 76 and 77 to the
solenoid of valve 69, causing this valve to shift so as to
retract its associated gate pin. Because conduit 78 leading
from limit switch 65 is connected to all switches 1, 2, 3 and
4, all four timers will be actuated and thus all shut-off
bushings will be opened. The degree of opening of each shut-
off bushing will depend however on the previous adjustment of
its gate pin as described above with respect to Figures 2 and 3.
The timers will all begin to run as material flows
into all four cavities. It should be noted that the gate pins
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~ill not be retracted by the pressure of the material, but by
the positive action of their individual fluid motors, so that
material can flow into all cavities under relatively low
injection pressure.
When the first cavity is filled with the optimum
amount of material, as determined during setup either by its
individual timer or by other means such as pressure-sensitive
transducers (not shown), the corresponding solenoid-operated
valve 69 will be shifted to its opposite position, thus
advancing its fluid motor piston 53 and corresponding gate pin
37 to its closed position. From that point on, the material
flowing into the single entry 24 will be able to fill the
remaining open cavities. When all cavities have been properly
filled as controlled in the manner described above, all gate
pins will have been closed and the molds may then be opened.
! The above-described method of individually controlling
the gates is also described and is claimed in the above-
identified parent application 335,543.
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Figure 5 shohs schematically a modified form o~ the inven-
tion in which a cycle counter 79 is provided for each gate pin
37, by connecting the counter at 81 to the timer 71 for such pin.
By presetting this counter, it may be used to disenable its timer
after a preselected number of gate pin openings has beén attained.
This ~ate pin will thereafter remain closed while the Temaining
gate pins operate. Thus inventory control for individual cavities
of a multiple cavity mold may be achieved. At the same time, the
counter may open the circuit to heater 32 for the coTresponding
shut-off bushing 17, by means of a temperature controller indi-
cated at 82. This will prevent degradation of material in the
inactive bushing.
More particularly, Figure 5 shows mold halves 12 and 13
with a switch 83 which closes in response to mold closing. This
switch is connected to counters 79 and 7ga for bushings 17 and
18 respectively. These are count-down counters which may be pre-
set for given figures and will disenable their respective timers
when they reach zero. Switches 84 may be provided for the counters,
which when moved to their "off" positions will byp~ss the counters.
A totalizer 85 may also be provided to count the total mold cycles.
Timers 71 and 71a control their respective solenoid-operated valves
69 through switches 1 and 2 as in the embodiment of Figure 4.
Counters 79 and 79a are also connected to bushing heater tempera-
ture controllers ~2 by connections 86 and switches 87. These
switches are individually movable to an "auto" position so that
~he counters can disenable the controllers, or to as "on" position
in which the heaters are always energized from a power source 88.
The power source also supplies heaters 89 for manifold 19 through
a switch 91 and temperature controllers 92. The power source for
solenoid-operated valves 69 is indicated at 93.
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Operation of the embodiment of Figure 5 will be similar to
~at of Figure 4, with the exception that, with any counteT 79
operative, it will count down the preset number of cycles and then
disenable its timer. This will cause the corresponding gate pin
to be closed, and its heater to be de-energized.
It will be noted that the invention ~ermits the use of
standard molding machines, the individual shut-off bushings in
the mold being made to any desired length and spacing rather
than being dictated by the requirements of a special machine.
The invention is thus useful not only for multiple cavity molds
but for molds with a single cavity where several bushings are
needed to fill the cavity. An example could be cavity for an
assymetrical part, where one portion of the cavity must be filled
at a different rate, or requires a bushing of different length,
than another portion.
I~hile it will be apparent that the preferred embodiments of
the invention disclosed are well calculated to fulfill the objects
above stated, it will be appreciated that the invention is sus-
ceptible to modification, variation and change without departing
from the proper scope or fair meaning of the subjoined claims.
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