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
1999-06-16
2002-04-02
Nguyen, Nam (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, C425S150000, C425S170000
Reexamination Certificate
active
06364650
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an injection apparatus.
2. Description of the Related 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.
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, and retracted so as to meter the resin.
There has been provided an injection apparatus for an electric injection molding machine in which an electric motor is used to advance and retract the screw.
FIG. 1
is a schematic view of a conventional injection apparatus used in an electric injection molding machine.
In
FIG. 1
, numeral
2
denotes an injection apparatus, and numeral
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 (the 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 (i.e. moved leftward and rightward in FIG.
1
). The rear end (the 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 ball screw shaft
8
is rotatably supported on the frame
4
in parallel with the screw
20
. The rear end of the ball 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 designed to rotate the ball screw shaft
8
. The front end of the ball screw shaft
8
is in screw engagement with a ball nut
5
a
fixed to the support member
5
. Accordingly, by driving the injection motor
9
and rotating the ball screw shaft
8
via the timing belt
7
b
, the ball nut
5
a
can be moved axially. A load cell
5
b
is disposed between the support member
5
and the ball nut
5
a.
In the injection apparatus
2
having the above-described structure, in a metering stage, the rotation generated by the driven metering motor
6
is transmitted to the screw
20
via the timing belt
7
a
, thereby retracting (i.e. moving rightward in
FIG. 1
) the screw
20
by a determined amount. At this time, resin is supplied from the hopper
21
b
, heated and melted within the heating cylinder
21
, and accumulated on the front side of the screw
20
.
Further, in an injection stage, the rotation generated by the driven metering motor
9
is transmitted to the ball screw shaft
8
via the timing belt
7
b
, so that the ball nut
5
a
and the support member
5
are advanced (i.e. moved leftward in
FIG. 1
) with the rotation of the ball screw shaft
8
. As a result, the screw
20
is also advanced, and the resin accumulated at the front side of the screw
20
is injected into the cavity of an unillustrated mold apparatus from the injection nozzle
21
a.
At this time, the force for advancing the ball nut
5
a
; i.e., the injection force imparted to the screw
20
, is detected by the load cell
5
b.
However, in the conventional injection apparatus
2
, since the injection force is generated with the rotation of the ball screw shaft
8
, the ball nut
5
a
receives a torque corresponding to the screw-engagement angle between the ball screw shaft
8
and the ball nut
5
a
. Therefore, accuracy in detection of the injection force by the load cell
5
b
is lowered.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above-mentioned problems in the conventional injection apparatus, and to provide an injection apparatus which can detect injection force with improved accuracy.
To achieve the above object, an injection apparatus according to the present invention comprises a cylinder member, an injection member, a first support member, drive means, a transmission shaft, a second support member, and load detection means. The injection member is disposed within the cylinder member such that the injection member can be advanced and retracted. The first support member supports the injection member such that the injection member can rotate. The transmission shaft is connected to the injection member such that the transmission shaft can rotate relative to the injection member and has a rotation transmission portion, to which rotation of the drive means is transmitted, as well as a motion conversion portion for converting rotational motion to linear motion. The second support member is adapted to allow relative rotation between the injection member and the transmission shaft. The load detection means is disposed between the first support member and the second support member.
In this injection apparatus, when the rotation of the drive means is transmitted to the transmission shaft via the rotation transmission portion, the rotational motion is converted to linear motion by the motion conversion portion, so that the injection member is advanced so as to perform injection. At this moment, the load detection means detects the injection force.
Since the load detection means is disposed between the first support member and the second support member, rotation of the injection member imparts no torque to the load detection means. Also, since the load detection means is connected to the transmission shaft via the second support member, rotation of the transmission shaft imparts no torque to the load detection means.
Therefore, accuracy in detection of injection force by the load detection means can be improved.
Another injection apparatus according to the present invention further includes a metering motor, and transmission means for transmitting rotation of the metering motor to the injection member.
Still another injection apparatus according to the present invention includes a heating cylinder, a screw, a support plate, an injection motor, a transmission shaft, a bearing box, and load detection means. The screw is disposed within the heating cylinder such that the screw can be advanced and retracted. The support plate supports the screw such that the screw can rotate. The transmission shaft is connected to the screw such that the transmission shaft can rotate relative to the screw and has a rotation transmission portion, to which rotation of the injection motor is transmitted, as well as a motion conversion portion for converting rotational motion to linear motion. The bearing box is adapted to allow relative rotation between the screw and the transmission shaft. The load detection means is disposed between the support plate and the bearing box.
In yet another injection apparatus according to the present invention, the rotation transmission portion is a spline shaft portion formed on the transmission shaft.
In yet another injection apparatus according to the present invention, the motion conversion portion is a ball screw shaft portion formed on the transmission shaft.
REFERENCES:
patent: 4755123 (1988-07-01), Otake
patent: 4758391 (1988-07-01), Shimizu et al.
patent: 4851171 (1989-07-01), Shimizu et al.
patent: 4879077 (1989-11-01), Shimizu et al.
pat
Arent Fox Kintner Plotkin & Kahn,PLLC
Luk Emmanuel
Nguyen Nam
Sumitomo Heavy Industrie's, Ltd.
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