Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
1998-11-06
2001-09-25
Heitbrink, Tim (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
C425S564000, C425S566000
Reexamination Certificate
active
06294122
ABSTRACT:
BACKGROUND
The present invention relates to pin movement control mechanisms in injection molding machines and more particularly to electrically powered actuating mechanisms for axial drive of pin mechanisms which are disposed in a melt flow channel in an injection molding apparatus. Hydraulic and pneumatic actuators have traditionally been used to control the movement of a pin used, for example in a valve, in injection mold apparati due to the high pressures under which molten polymer is injected into the mold cavity such pressures typically being in excess of 50 MPa, e.g. around 100 Mpa and in high pressure molding in excess of 200 Mpa. Such conventional actuators are complex in design, maintenance intensive, bulky in size and relatively undesirable in environments of higher cleanliness.
SUMMARY OF THE INVENTION
In accordance with the invention therefore, in injection molding machines and processes, there is provided an axially slidable pin which is driven in a predetermined path of axial travel by an actuator which is driven by electrical power, the actuator being drivably interconnected to the pin. The actuator may comprise a mechanism which is drivably interconnected to the rotor of an electrically powered motor (either coaxially along an axis of the rotor or via some other non-coaxial interconnection such as a bevel gear, worm gear, rack/pinion/gear, multiple gear or other interconnection) the driven actuator, in turn, driving movement of the pin. A frameless motor or a motor having a shaft may be utilized. The apparatus preferably includes a mechanism for absorbing forces which may be transmitted from the pin to the rotor of the motor along its axis. The invention may include a controller which receives signals generated by one or more sensors which sense selected conditions of the molten plastic, the controller utilizing the signals according to a predetermined algorithm and controlling the drive of the electrically driven actuator according to the algorithm.
Apparatuses and methods according to the invention may or may not include a motor drive controller and the controller may have an algorithm which does or does not utilize signals/data which are representative of sensed conditions of the melt or the machine components.
In the most preferred embodiments described herein, axial forces to which the pin is subjected are transmitted to the actuating mechanism without loading the rotor of the drive motor along its axis. In embodiments where the motor rotor is coaxially aligned with the axis of the reciprocating pin, a force absorbing mechanism is preferably used to absorb the load which would otherwise be transmitted to the motor along its axis.
More particularly, there is provided in an injection molding machine, an apparatus for controlling movement of a pin comprising:
a plastic melt flow channel having an output end for delivering molten plastic injected into the channel under pressure to a mold cavity, wherein the pin comprises an elongated rod having an axis and an end, the pin being slidably mounted within the channel for movement along its axis within the channel,
an electrically driven motor drivably interconnected to an actuating mechanism, wherein the actuating mechanism is drivably interconnected to the end of the pin, the motor being controllably drivable to drive the pin through movement along its axis within the channel.
The motor may include a rotatably driven rotor which translates motion to the pin to drive the pin along its axis without rotation. The pin is typically subjected to forces along its axis wherein the actuating mechanism is interconnected to the end of the pin such that the axial forces to which the pin is subjected are transmitted between the pin and the actuating mechanism without absorption of the axial forces. The apparatus may include a force absorbing member which absorbs forces transmitted to the rotor of the motor along its axis. The actuating mechanism may comprise a screw and a complementary nut screwably engaged with each other, at least one of the screw and the nut being drivably interconnected to the motor to travel along a predetermined path of travel, the pin being simultaneously driven along its axis through a path of travel according to the predetermined path of travel of the screw or the nut.
The motor may be connected to a controller having a program for driving the movement of the actuating mechanism according to one or more sensed conditions of the molten plastic or the injection molding machine. The controller may include a PID (proportional, integral, derivative) controller. Protocols other than PID may be utilized. The program for driving the movement of the actuating mechanism typically includes an algorithm utilizing a value representative of one or more of the pressure, temperature, viscosity and flow rate of the molten plastic, the position of a component of the machine and the time or time lapse of operation of the machine or a component of the machine. The apparatus may include a sensor which senses a selected condition of the molten plastic or the injection molding machine and which generates signals representative of the sensed property, the controller having a program which controls the motor according to the generated signals. The apparatus may also include a recorder or sensor or monitor which measures, records or monitors the position of a component of the machine or the time or time lapse of the operation of the machine or a component of the machine.
There is further provided, in an injection molding machine, a plastic melt flow control valve apparatus comprising:
a plastic melt flow channel having an output end for delivering molten plastic injected into the channel under pressure to a mold cavity;
an elongated valve pin having an axis and an end, the pin being slidably mounted within the channel for movement along its axis within the channel to control flow of the molten plastic;
an electrically driven motor drivably interconnected to an actuating mechanism, wherein the actuating mechanism is interconnected to the end of the pin, the motor being controllably drivable to drive the pin through movement along its axis within the channel.
There is further provided in an injection molding machine having a plastic melt flow channel with a pin slidably mounted within the channel, wherein the channel has an output end for delivering molten plastic injected into the channel under pressure to a mold cavity, and wherein the pin comprises an elongated rod having an axis and an end, the pin being slidably mounted for movement along its axis within the channel, a method for controllably driving movement of the pin along its axis comprising:
drivably interconnecting a rotatable rotor of an electrically driven motor to an actuating mechanism which is drivably movable along a predetermined path of travel;
interconnecting the actuating mechanism to the end of the pin such that movement of the actuating mechanism along its predetermined path of travel simultaneously moves the pin along its axis according to a predetermined path of travel;
controllably driving the motor to controllably drive the actuating mechanism and to controllably drive the pin through its predetermined path of travel within the channel.
The rotor of the motor most preferably translates rotational force to the pin to move the pin along its predetermined path of travel without rotation of the pin. The method may comprise interconnecting the actuating mechanism to the end of the pin such that the axial forces to which the pin is subjected are transmitted between the pin and the actuating mechanism with or without absorption of the forces.
The method may further comprise sensing one or more conditions of the molten plastic selected from the group consisting of pressure, temperature, viscosity, force and flow rate of the molten plastic or recording or measuring one or more of the position of a component of the machine or the time or time lapse of the operation of the machine or a component of the machine and controlling the drive of the motor according to
Kazmer David
Lee Christopher
Moss Mark
Rinderle James R.
Heitbrink Tim
Synventive Molding Solutions, Inc.
Wolf Greenfield & Sacks P.C.
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