Molding apparatus

A molding apparatus is provided for molding one or more liquid molding materials, such as thermoplastic or thermosetting resins and the like which are controllably flowed into a closed mold cavity wherein the instant rate of flow and pressure of the molding material are predeterminately varied during a molding cycle so as to control and predetermine the shape and physical characteristics of the articles molded thereby. In one form, a closed loop automatic control system is employed to predeterminately control and vary the rate of flow of molding material to a mold cavity so as to optimize the molding procedure and predetermine the physical characteristics of the molded article.

SUMMARY OF THE INVENTION 
This invention relates to a molding apparatus for molding liquid molding 
materials such as plastic resins which solidify after being injected into 
a mold by the addition of heat thereto or a catalyst, as in the case of a 
thermosetting resin or by the removal of heat therefrom, as in the case of 
a molten thermoplastic resin. Automatic control is effected of such 
molding variables as the rate of flow of components of a molding material, 
one or more molding materials, in certain instances, a decorating material 
together with a molding material, to the cavity of a mold wherein control 
of the molding operation including a plurality of variables thereof, is 
automatically effected. 
Heretofore, most molding operations, such as low or high pressure injection 
molding, die casting and other forms of molding molten of liquid polymers 
and metals, have been performed wherein the molding material is injected 
into the mold at a substantially constant rate of flow by driving an 
injection screw or piston at substantially constant speed or by suddenly 
opening a valve in the line between the injector and a source of 
pressurized molding material such as a quantity thereof located in an 
accumulator. Articles molded by the described procedure in which flow rate 
or pressure is substantially constant after the initial surge of molding 
material through the injector, have suffered certain shortcomings in 
structure and appearance, the severity and characteristics of which 
shortcomings is a function of the characteristics of the molding material, 
the shape of the mold cavity, the viscosity of the molding material and 
the rate of flow thereof into the mold. 
The instant invention is concerned with a molding apparatus and method for 
molding articles in a mold wherein the rate of flow of molding material is 
controlled and may be predeterminately varied during a molding cycle so as 
to obtain the optimum or desired characteristics of the molded article. In 
one form, an open loop control system is provided wherein an analog signal 
is generated as reproduced from a recording thereof or from any suitable 
analog signal generating means and the signal is applied to control a 
servo device such as a motor operable to open and close a valve in the 
molding material inlet line or a feeding device such as a screw or piston. 
In a closed loop control system, an analog signal is generated at a known 
time in a molding cycle as an input reference signal and a feedback signal 
is generated by a transducer, such as a pressure transducer, disposed in 
the inlet line or the mold cavity wall. The feedback signal is bucked 
against the reference signal in a comparator and a difference signal is 
generated which is applied to control the servo operating the pump, screw 
or valve controlling rate of flow. 
Accordingly it is a primary object of this invention to provide a new and 
improved molding apparatus and method for molding molten materials by 
injection into a cavity of a mold wherein the rate of flow of injection 
material may be predeterminately varied during each molding cycle so as to 
variably increase and decrease the pressure of the flowing material and 
thereby effect control over and predetermine the physical characteristics 
of the molded article. 
Another object is to provide a molding apparatus which is automatic in its 
molding operation and wherein the molding cycle variables are 
predeterminately controlled by electrical signals which may not only be 
repeated from cycle to cycle but may be easily changed to vary the 
physical characteristics of the same molded shape, to optimize the 
physical characteristics of a plurality of different shaped articles 
formed in different molds or to permit experiments to be performed without 
difficulty so as to obtain moldings of optimum characteristics or having 
characteristics which are predetermined. 
Another object is to provide a molding apparatus employing feedback signal 
generating means associated with the mold itself to assure that a 
commanded flow rate is being carried out during molding. 
Another object is to provide a control system for an injection molding 
machine capable of predeterminately controlling substantially all molding 
variables. 
Another object is to provide a computer controlled molding apparatus. 
Another object is to provide a hybrid molding control system employing 
analog signals for controlling rate of flow of molding material and 
digital or pulse signals for controlling other variables such as mold 
closure and opening. 
With the above and such other objects in view as may hereinafter more fully 
appear, the invention consists of the novel constructions, combinations 
and arrangements of parts as will be more fully described and illustrated 
in the drawings but it is to be understood that changes, variations and 
modifications may be resorted to which fall within the scope of the 
invention as claimed.

Referring now to the drawings, there is shown in FIG. 1 a control system 
for a molding apparatus 10 which is operative to controllably feed one or 
more molding materials to the cavity 31 of a two-part mold 28 composed of 
mold sections 29 and 30, at least one of which is movable with respect to 
the other to effect the opening and closing of the mold. In FIG. 1, a 
servo 40, such as a hydraulic actuator or cylinder is operative to open 
and close the mold 28 by lineally moving the mold section 30 with respect 
to the mold section 29 a degree in opening to permit removal of the molded 
article from the mold cavity 31. The actuator 40 is preferably operative 
in response to signals generated by a program controller or computer which 
will be described and which also controls other variables associated with 
the molding apparatus such as the injection of molding material, mass rate 
of flow of said material, the flow of heat transfer fluid through the mold 
walls, the flow of decorating material to the mold and any auxiliary 
equipment associated with the molding operation. 
In FIG. 1, two closed loop control systems are illustrated, one to 
predeterminately control the injection and flow of a molding material into 
the mold cavity and the other for controlling the flow of a decorating 
material or a second molding material to the mold cavity. Control of all 
molding variables including the direct control of the servos or valves for 
operating mold actuators, is effected by means of a master controller 11 
which, in a preferred form of the invention, comprises a sequential signal 
generator having a plurality of outputs 12 including at least one output 
extending to each of the servo controls and the closed loop control 
systems for controlling the flow of molding material and, in those cases 
where applicable, the flow of decorating material to the mold. The 
sequential signal generator may, in its simplest form, comprise a 
multi-circuit, recycle timer or, in a more complex form, a digital 
computer operative to generate command control signals and to apply same 
to the inputs of the various controllers of the system. In the form 
illustrated in FIG. 1, the master controller 11 preferably comprises means 
for generating a plurality of analog control signals and pulse signals on 
the outputs 12 thereof, such as a magnetic recorder containing an endless 
recording member such as an endless belt, drum or disc having a plurality 
of record tracks at least certain of which have respective analog control 
signals recorded thereon to variably control devices such as platons or 
screws for feeding molding materials and, in certain instances, decorating 
materials to the mold. 
Shown coupled to the inlet passageway or sprue 32 of the mold is an 
injection nozzle 24N extending from an injection head 24 terminating a 
chamber 25 containing molding material which is heated and dispensed into 
interior volume 24' of injection head 24 and a piston 23 by means of a 
motor 26 driving a feed screw located within chamber 25. Injection molding 
material may be rendered molten in chamber 25 and fed by means of an 
extrusion screw through a solenoid operated valve 27 located between 
chambers 25 and 24. When the piston 23 is retracted, motor 26 may be 
operated by means of a signal generated by signal generator 11 to drive 
the screw or piston located in chamber 25 and valve 27 may be opened by a 
second signal generated as reproduced from a second track of the signal 
generator 11 so as to admit a predetermined quantity of molten molding 
material to the volume 24'. Thereafter, the piston 23 is advanced at a 
predetermined velocity which may remain constant during the molding cycle 
or may vary according to the characteristics of the analog signal 
generated by the sequential signal generator 11 and utilized to control 
the operation of the means driving said piston. Forward movement of piston 
23 is operative to force molten molding material in the volume 24' out of 
the nozzle 24N and into the cavity 31 of the mold 28. The actuator 19 for 
the piston 23 is a hydraulic cylinder having an output shaft 20 connected 
to the piston 23, said output shaft being variably projectable in a manner 
such that its position and velocity may be predeterminately controlled by 
an analog signal generated by signal generator 11 as reproduced from a 
particular track, for example, of the magnetic recording member therein. 
The hydraulic cylinder 19 is automatically controlled by an 
electro-hydraulic controller 13 composed of an electric stroker for 
controlling the position of a slide block of a variable displacement 
hydraulic pump 16 through a hydraulic stroker 15. The characteristics of 
the variable displacement hydraulic pump 16 are such that the pump may 
pump hydraulic fluid in either direction so that the position as well as 
the direction of the piston 25 connected to the shaft 20 of the hydraulic 
cylinder 19 will be a function of the amplitude of the analog signal 
reproduced from the channel of signal generator 11 which is used to 
control the electro-hydraulic controller 13. 
A feedback signal indicative of the position of the shaft 20 of the 
hydraulic cylinder 19 is generated by a variable potentiometer 21 having a 
wiper arm which is coupled by means of gears or other suitable means to 
rotate respectively in a clockwise and counterclockwise direction with the 
forward and reverse movement of shaft 20. The potentiometer 21 generates a 
feedback signal which is a function of the position of shaft 20. The 
feedback signal is bucked against the reference signal generated by 
sequential signal generator 11 on a line 12a extending to a comparator 22, 
such as a summing amplifier. The difference signal output of the 
comparator 22 is used to control the electric stroker 14. The electric 
stroker, in turn, controls a valve plunger through precision gearing and 
effects control of the hydraulic stroker 15 which controls the output of 
the hydraulic pump 16. The output line 17 of the hydraulic pump is 
connected to the input 18 of the hydraulic cylinder 19. The stroke in 
position of the output shaft 20 of cylinder 19 is therefore 
predeterminately controlled in accordance with the characteristics of the 
analog signal generated on the input 12a to the comparator 22. Thus, by 
varying the characteristics of the analog signal recorded in the 
sequential signal generator 11, the movement of piston 23 may be 
predeterminately varied so as to predeterminately determine or vary the 
velocity and rate of flow of molding material forced by said piston 
through the injection nozzle 24N into the mold cavity 31 as further 
defined in Ser. No. 416,219. 
One or more additional injection nozzles operatively coupled to the input 
sprue or passageway 32 or to other passageways extending to the cavity 31 
of the mold may extend from respective other feed chambers similar to 24 
in which drive pistons or screws are movable by means similar to that 
described above for operating piston 23 so as to predeterminately control 
the flow of one or more other molding materials into the mold cavity 31 in 
accordance with the flow of the molding material through nozzle 24N. By 
variably and predeterminately controlling the flow of said molding 
material or materials, the characteristics of an article molded in the 
cavity 31 of the mold may be predeterminately controlled and part 
shrinkage may be controlled, minimized or eliminated thereby. 
Also shown in FIG. 1 is a second injection apparatus for molding or 
decorating material. This second apparatus is composed of a cylinder 25' 
containing a piston 26' for forcing molding or decorating material 
disposed within the cylinder 25' through an output line 27' which extends 
to a passageway 34 extending through the wall of the mold member 29 and 
having a porous plug 35 disposed within said passageway and defining a 
portion of the wall of the molding cavity. Decorating material may thus be 
forced from cylinder 25' to the passageway 34 and through the porous 
member 35 disposed therein at a predetermined time during a molding cycle 
such that a portion of said material is deposited on and decorates the 
surface of the molding formed in the mold. 
The piston 26' of cylinder 25' is connected to the output shaft of a 
hydraulic cylinder actuator 36 which is similar in operation to the 
actuator 19 described and is controlled in its operation in a manner 
similar to the manner in which cylinder 19 is controlled. Notation 13' 
refers to an electro-hydraulic control block having components similar to 
those found in block 13 and comprising a comparator, an electric stoker, a 
hydraulic stroker, a variable displacement pump and a feedback 
potentiometer riding on the shaft of the cylinder 36 for providing a 
feedback signal to assure that the operation defined by the analog signal 
generated on the input to the controller 13' is effected. 
Depending on the location of the analog signal recorded on the record 
member of the sequential signal generator 11 and utilized to control the 
operation of the cylinder 36, the material disposed within cylinder 26' 
may be predeterminately timed and controlled in its rate of flow into the 
porous member 35 or mold cavity in accordance with the flow of primary 
molding material through nozzle 24N. 
Also shown in FIG. 1 is a pressure transducer 39 which is secured in the 
mold wall and located so as to have its active element compressed, either 
directly or indirectly, by means of the pressure of the molding material 
injected into the mold cavity. The transducer 39 is connected to the 
control input of a solenoid operated valve 42 which, upon becoming 
actuated by a signal received from said transducer, suddenly admits a 
fluid such as air, decorating fluid or molding material from an 
accumulator 43 to a line 44 for either pressurizing the porous member 35 
to prevent the flow of primary molding material through said porous member 
or for admitting decorating or molding material to the mold. The signal so 
generated by the transducer 39 may also be operative to close a valve in 
the line extending to the porous member 35 to prevent the backflow of 
molding material through said porous member. If decorating material is 
admitted to the input line and a valve in the line is closed by a signal 
received from the transducer 39, said fluid material being substantially 
incompressible, prevents molding material from entering and flowing 
through the porous member 35 in the input line extending thereto. 
Thus, it is seen that the apparatus of FIG. 1 may be operated in a variety 
of different modes, depending on the characteristics of the molding 
material or materials admitted to the mold and a decorating material, if 
applicable, admitted to the mold or a porous portion of the wall of the 
mold cavity as described. 
It is noted that the apparatus of FIG. 1 may be used for producing or 
decorating composite articles in a single mold which articles may be 
injection molded or die cast of two or more of such materials as plastics, 
ceramics or metals or combinations of these materials. 
In FIG. 2 is shown a modified form of control system for a molding 
apparatus which is a modified form of that shown in FIG. 1. A master 
controller 50 has a plurality of output lines 51 on which are generated 
respective control signals in timed relationship to each other, which 
signals are fed to forward, stop and reverse controls designated F, S and 
R of various servo motors denoted 52-58 for controlling the various 
devices associated with the molding apparatus. A first servo motor 52, for 
example, controls the opening and closing of one mold part with respect to 
the other to permit the removal of the molded article from the mold cavity 
and to close the mold with a sufficient clamping pressure to permit 
molding material to be molded therein. A second servo 53 controls the 
delivery of the molding material by predeterminately operating a piston or 
screw feeding molten molding material to the mold cavity through an 
injector as described. A further servo similar to 53 may also be employed 
to flow a second molding material to the mold cavity through the same 
inlet through which the first molding material is flowed or through a 
second inlet to the mold. 
A third servo 54 is operative to predeterminately control the flow of a 
decorating material to a passageway in the mold, as described, having a 
porous member disposed within the mold cavity wall and defining the 
characteristics of the decoration to be printed on the surface of the 
molding formed in the mold. 
Another servo member 55 is used to control a valve for admitting back 
pressure air to the inlet line through which decorating material is flowed 
to the mold so as to prevent backflow of molding material through said 
line. 
The servo motors 57 and 58 are utilized respectively to control the flow of 
heat transfer fluid through the mold Motor 57 is operative, when activated 
by a signal derived from the computer 50 to pump hot liquid or gas through 
the passageways 49 provided in the mold wall while motor 58, when 
activated by a signal generated by the computer 50 is operative to pump 
coolant or a refrigerant through said mold wall passageways. Thus if a 
thermosetting resin is injected into the mold, the mold wall may be 
predeterminately heated prior to and/or during the filling of the mold 
cavity with said resin. Thereafter the computer or controller 50 may be 
operative to control motor 58 to pump refrigerant or coolant liquid 
through the mold passageways to rapidly cool the mold prior to removing 
the part from the mold. Certain thermoplastic resins, such as high 
temperature resins, may also provide better molded parts when the mold 
wall is predeterminately heated prior to the injection thereof into the 
mold cavity. The computer or self-recycling controller 50 may thus be 
programmed to control not only the operation and timing of the servos used 
to pump heat transfer liquid through the mold but also the rate of flow of 
said fluids by metering same or controlling the operating speed of the 
motors. 
The apparatus described may also be utilized to advantage in the art of die 
casting or injection molding metals where the quality of the finished 
casting or metal molding is directly related to such process variables as 
the pressure applied to the injected metal, the temperature of the metal, 
the temperature of the die, and the fill time required for a given die 
cavity. These variables generally require close scruteny and are varied at 
present by a skilled operator based on his experience by manually 
adjusting various controls therefore. Accordingly, a further controller 59 
is provided for variably controlling temperature of the molding material 
and is operated by a signal derived from the computer 50 and/or a sensor 
adapted to measure said temperature and generates a feedback signal to be 
bucked against a command signal generated by the computer. The resulting 
difference signal may be used, for example to control a motor used to 
control a variable potentiometer for variably controlling the voltage 
applied to an induction or resistance heating means for a furnace or other 
means for heating the molding material so as to predeterminately heat same 
prior to injection or flow into the mold. 
Further adaptive control means applicable to the apparatus of FIGS. 1 and 2 
may be provided in the form of sensors or transducers disposed within or 
coupled to the supply chamber 25, the accumulator or injection chamber 
24', the mold cavity 31, the mold wall or passageways 49 therein and in 
any auxilliary means associated with the described molding apparatus for 
generating feedback or adaptive control signals which vary with variations 
in such process variables as molding material temperature prior to 
injection, molding material flow during injection into the mold or to the 
accumulator, mold temperature, molding material pressure during flow into 
the mold and within the mold and the temperature of the molding while in 
the mold. Said transducer generated signals may be bucked against 
reference signals generated by the computer in a comparator device such as 
a summing amplifier applied to control the servo or other device utilized 
to effect predetermined changes in the variable being controlled for 
predeterminately controlling same. 
When two or more molding materials are fed to a mold cavity the 
temperature, pressure and flow of each may be monitored during the 
injection operation by suitably placed sensors as described which may 
generate feedback signals for predeterminately controlling the flow of 
each by the means described above so as to predeterminately dispose each 
material in the mold with respect to the other material and thereby 
predetermined the locations of said materials in the finished molding.