Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Feed control of material en route to shaping area
Reexamination Certificate
1998-11-13
2001-10-30
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Feed control of material en route to shaping area
C425S149000
Reexamination Certificate
active
06309203
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an injection apparatus for a motor-driven injection molding machine. In particular, it relates to an improvement that facilitates the control of back pressure during charging process.
2. Description of the Related Art
FIG. 7
shows an injection apparatus of a conventional motor-driven injection molding machine. The reference numeral
1
denotes an injection apparatus. A barrel unit
3
which is fed with plastic material is mounted on an injection carriage
2
. The barrel unit
3
includes a heated barrel having an internal elongated cylindrical bore. A screw
4
is rotatably and axially movably disposed in the cylindrical bore of the heated barrel
3
.
A ball screw
5
extends coaxially and integrally from a rear end portion of the screw
4
. A spline shaft
6
is integrally connected to the rear end of the ball screw
5
.
An injection motor
7
which is for use in the injection process and drives the ball screw
5
is installed in the injection carriage
2
. A charging motor
8
which is for use in the charging process and drives the spline shaft
6
is as well installed in the rear end of the injection carriage
2
. A rotor
9
of the injection motor
7
is designed to serve as a ball screw nut that engages with the ball screw
5
. And a rotor
10
of the charging motor
8
is designed to serve as a spline nut which the spline shaft
6
is slidably fitted therethrough. A numerical control unit
11
controls the operation of the injection motor
7
and charging motor
8
so that the screw
4
moves forwardly in the injection process, or rotates in the charging process.
During the charging process, the spline shaft
6
permits the transmission of the rotation of the charging motor
8
to the screw
4
integral with the spline shaft
6
and ball screw
5
. The screw
4
rotates and plasticizes the material fed into the barrel
3
. The melt material accumulates in front of the screw
4
, forcing back the screw
4
rearwardly.
During the injection process, the combination of the ball screw
5
and ball nut
9
converts the rotation of the injection motor
7
to the liner motion which causes the screw
4
to move forwardly(the leftward direction in the figure), whereby the screw
4
injects the molten material accumulated in front of the screw
4
into a mold cavity. The numerical control unit
11
controls the injection motor
7
to rotate and controls the charging motor
8
to keep from rotating, so as to enable the screw
4
to move forwardly.
The movement of the screw
4
in the charging process consists of the rotation for plastication and the retreat motion caused by the pressurized molten material accumulated in front of the screw
4
. The rotation of the screw
4
simultaneous with retreat is properly achieved, in conjunction with the injection motor
7
to control of the back pressure to be applied on the screw
4
.
However, in this prior-art injection apparatus, the ball screw
5
is made integral with the spline shaft
6
and it is so arranged that the charging motor
8
rotates the spline nut
10
fitted onto the spline shaft
6
. Therefore, while the charging motor
8
rotates the spline shaft
6
to cause the screw
4
to rotate, the ball screw
5
rotates inevitably. This inevitable rotation of the ball screw
5
brings the screw
4
to move rearwardly, regardless of the amount of the molten material forced forwardly by the rotating screw
4
.
The prior-art injection apparatus provided with the charging motor
8
having such a structure that the spline shaft
6
passes through the rotor
10
involves following drawbacks to control the back pressure. The rotation of the rotor
10
prevents the spline shaft
6
from slipping axially through the rotor
10
. That needs to apply a appropriate back pressure to the screw
4
to cause it to retreat at the velocity corresponding to the feed rate of the molten material. For that reason, it is difficult to control the charging motor
8
and injection motor
7
with the rotation of the former being synchronized with that of the latter. That fails in the precise control of the back pressure applied to the screw
4
. As a result, The screw
4
is forced to retreat only by the pressure of the molten material.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an injection apparatus for a motor-driven injection molding machine which enable to remove therefrom the above-described drawbacks that make it difficult to control the charging motor and injection motor synchronously, and to achieve the precise control of the back pressure applied to the screw.
According to a first aspect of the present invention, an injection apparatus for a motor-driven injection molding machine having a barrel unit for heating and plasticating polymer material and a screw disposed in the barrel unit rotatably and movably in the axial direction comprises a first rotating shaft having one end connected to a rear end of the screw, a charging motor for driving the first rotating shaft for rotation, a ball screw mechanism consisting of a second rotating shaft having a threaded rod portion, and a threaded nut member engaging with the threaded rod portion, an injection carriage having a front plate for mounting the barrel unit thereon, and a rear plate for supporting the second rotating shaft at the rear end thereof, an injection motor for driving the ball screw mechanism, and an intermediate mount plate, disposed movably between the front plate and the rear plate, for linking the first rotating shaft to the second rotating shaft coaxially with a predetermined distance spaced apart between the rear end of the first rotating shaft and the front end of the second rotating shaft.
According to a second aspect of the present invention, an injection apparatus for a motor-driven injection molding machine having a barrel unit for heating and plasticating polymer material, and a screw disposed in the barrel unit rotatably and movably in the axial direction comprises a first rotating shaft having one end connected to a rear end of the screw, a ball screw mechanism consisting of a second rotating shaft having a threaded rod portion, and a threaded nut member engaging with the threaded rod portion, an injection carriage having a front plate for mounting the barrel unit thereon, and a rear plate for supporting the second rotating shaft at the rear end thereof, an intermediate mount plate, disposed movably between the front plate and the rear plate, for linking the first rotating shaft to the second rotating shaft coaxially with a predetermined distance spaced apart between the rear end of the first rotating shaft and the front end of the second rotating shaft, a charging motor for driving the first rotating shaft for rotation, and mounted on the intermediate mount plate, and an injection motor for driving the threaded nut member of the ball screw mechanism for rotation, and mounted on the rear plate of the injection carriage.
According to a third aspect of the present invention, an injection apparatus for a motor-driven injection molding machine having a barrel unit for heating and plasticating polymer material, and a screw disposed in the barrel unit rotatably and movably in the axial direction, comprises a first rotating shaft having one end connected to a rear end of the screw, a second rotating shaft having a threaded rod portion, a threaded nut member engaging with the threaded rod portion, an injection carriage having a front plate for mounting the barrel unit thereon, and a rear plate with the threaded nut member fixed thereon, an intermediate mount plate, disposed movably between the front plate and the rear plate, for linking the first rotating shaft to the second rotating shaft coaxially with a predetermined distance spaced apart between the rear end of the first rotating shaft and the front end of the second rotating shaft, a charging motor for driving the first rotating shaft for rotation, and mounted on the intermediate mount plate, and an injection mot
Koike Jun
Tamaki Masahiro
Heitbrink Tim
Pillsbury & Winthrop LLP
Toshiba Kikai Kabushiki Kaisha
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