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
2000-02-10
2003-02-11
Silbaugh, Jan H. (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
C264S040700, C425S149000, C425S167000, C425S542000
Reexamination Certificate
active
06517336
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an injection molding machine.
BACKGROUND ART
Conventionally, in an injection molding machine, resin heated and melted in a heating cylinder is injected into the cavity of a mold apparatus under high pressure so that the cavity is filled with the resin. The molten resin is then cooled and solidified so as to obtain a molded article.
For performing such molding operation, the injection molding machine includes a mold clamping apparatus and an injection apparatus. The mold clamping apparatus is provided with a stationary platen and a movable platen. The movable platen is advanced and retracted by a mold clamping cylinder, to thereby perform mold closing, mold clamping, and mold opening.
The injection apparatus includes a heating cylinder for heating and melting resin supplied from a hopper, and an injection nozzle for injecting the molten resin. Further, a screw is disposed within the heating cylinder such that the screw can be rotated and can be advanced and retracted. The screw is advanced so as to inject the resin from the injection nozzle, and is retracted so as to meter the resin.
In order to advance and retract the screw, a motor-driven injection apparatus is provided.
FIG. 1
is a schematic view of a conventional injection apparatus.
In
FIG. 1
, reference numeral
2
denotes an injection apparatus, and
4
denotes a frame of the injection apparatus
2
. A heating cylinder
21
is fixedly provided in front (left side in
FIG. 1
) of the frame
4
, and an injection nozzle
21
a
is provided at the front end (left-side end in
FIG. 1
) of the heating cylinder
21
. A hopper
21
b
is disposed on the heating cylinder
21
, and a screw
20
is disposed within the heating cylinder
21
such that the screw
20
can be rotated and can be advanced and retracted (moved leftward and rightward in
FIG. 1
, respectively). The rear end (right-side end in
FIG. 1
) of the screw
20
is rotatably supported by a support member
5
.
Attached to the support member
5
is a metering motor
6
having a speed reduction mechanism. The rotation of the metering motor
6
is transmitted to the screw
20
via a timing belt
7
a.
Further, a screw shaft
8
is rotatably supported in parallel with the screw
20
. The rear end of the screw shaft
8
is connected, via a timing belt
7
b,
to an injection motor
9
having a speed reduction mechanism. That is, the injection motor
9
is adapted to rotate the screw shaft
8
. The front end of the screw shaft
8
is in screw engagement with a nut
5
a
fixed to the support member
5
. Accordingly, when the injection motor
9
is driven, the nut
5
a
can be moved axially through rotation of the screw shaft
8
via the timing belt
7
b.
In the injection apparatus
2
having the above-described structure, during a metering stage, the metering motor
6
is driven in order to rotate the screw
20
via the timing belt
7
a,
thereby retracting the screw
20
by a predetermined distance (rightward in FIG.
1
). At this time, resin is supplied from the hopper
21
b,
heated and melted within the heating cylinder
21
, and accumulated forward of the screw
20
as the screw
20
retracts.
Further, during an injection stage, the injection motor
9
is driven in order to rotate the screw shaft
8
via the timing belt
7
b,
so that the nut
5
a
and the support member
5
are moved with the rotation of the screw shaft
8
. As a result, the screw
20
is advanced (moved leftward in FIG.
1
), and the resin accumulated forward of the screw
20
is injected from the injection nozzle
21
a.
However, the injection apparatus
2
has the following drawbacks. That is, in the injection apparatus
2
, the metering motor
6
and the injection motor
9
must be driven during the metering stage and the injection stage, respectively. Further, rotation of the metering motor
6
and rotation of the injection motor
9
are transmitted to the screw
20
via speed reduction mechanisms, pulleys, etc. Therefore, mechanical efficiency is comparatively low, and inertia is comparatively high. As a result, during the injection stage, reaching an initial injection speed and changing the injection speed require a comparatively long period of time and a comparatively large torque. Further, the time required to proceed from the injection stage to the pressure holding stage is comparatively long.
In order to overcome the above-described drawbacks, there has been provided a built-in-motor-type injection apparatus in which a screw, an injection motor, and a metering motor are disposed on a common axis.
FIG. 2
is a sectional view of such a conventional built-in-motor-type injection apparatus.
In
FIG. 2
, reference numeral
12
denotes a heating cylinder, and an injection nozzle
12
a
is provided at the front end (left-side end in
FIG. 2
) of the heating cylinder
12
. A screw
22
is disposed within the heating cylinder
12
such that the screw
22
can be rotated and can be advanced and retracted (moved leftward and rightward in FIG.
2
).
The screw
22
has a screw head
22
a
at its front end. The screw
22
extends rearward (rightward in
FIG. 2
) within the heating cylinder
12
, and is connected at its rear end (right-side end in
FIG. 2
) to a first spline shaft
63
.
Therefore, during a metering stage, when the screw
22
is retracted (moved rightward in
FIG. 2
) by a determined distance, while being rotated, resin in the form of pellets is supplied from an unillustrated hopper, heated and melted within the heating cylinder
12
, and accumulated forward (leftward in
FIG. 2
) of the screw head
22
a
as the screw
22
retracts.
Further, during an injection stage, when the screw
22
is advanced (moved leftward in FIG.
2
), the resin accumulated forward of the screw head
22
a
is injected from the injection nozzle
21
a
and charged into a cavity of an unillustrated mold apparatus.
A drive section casing
11
is fixed to the rear end of the heating cylinder
12
. A metering motor
44
is disposed at the front portion (left-side portion) of the drive section casing
11
and an injection motor
45
is disposed at the rear portion (right-side portion) of the drive section casing
11
such that the metering motor
44
and the injection motor
45
share a common center axis. The metering motor
44
comprises a stator
46
and a rotor
47
, and the injection motor
45
comprises a stator
48
and a rotor
49
.
The rotor
47
is supported to be rotatable relative to the drive section casing
11
. Specifically, a hollow first rotor shaft
56
is fixedly fitted into the rotor
47
, and the first rotor shaft
56
is supported by bearings
51
and
52
.
Similarly, the rotor
49
is supported to be rotatable relative to the drive section casing
11
. Specifically, a hollow second rotor shaft
57
is fixedly fitted into the rotor
49
, and the second rotor shaft
57
is supported by bearings
53
and
54
.
The screw
22
can be retracted, while being rotated, through drive of the metering motor
44
. In order to enable this movement, a first spline nut
62
is fixed to the front end of the first rotor shaft
56
; a first spline shaft
63
is in spline-engagement with the first spline nut
62
; and the screw
22
is fixed to the front end of the first spline shaft
63
. Therefore, when the rotor
47
is rotated through drive of the metering motor
44
, rotation of the rotor
47
is transmitted to the screw
22
, so that the screw
22
rotates. At this time, the first spline shaft
63
is retracted relative to the first spline nut
62
, so that the screw
22
is retracted. It is to be noted that when the screw
22
is retracted, back pressure is applied to the screw
22
against pressure generated by the resin.
Further, the screw
22
can be advanced through drive of the injection motor
45
. In order to enable this movement, an annular bearing retainer
64
is fixed to the rear end of the second rotor shaft
57
; and a ball screw shaft
65
is inserted into and fixed to the bearing retainer
64
. The ball screw shaft
65
is supported to be rotatab
Emoto Atsushi
Hiraga Noritsugu
Luk Emmanuel
Silbaugh Jan H.
Squire Sanders & Dempsey LLP
Sumitomo Heavy Industrie's, Ltd.
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