Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting – Positioning of a mold part to form a cavity or controlling...
Reexamination Certificate
1999-08-31
2002-08-13
Heitbrink, Jill L. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
Positioning of a mold part to form a cavity or controlling...
C264S328110, C425S135000, C425S569000, C425S574000
Reexamination Certificate
active
06432333
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nozzle touch apparatus for an injection molding machine.
2. Description of the Related Art
Conventionally, an injection molding machine comprises an injection apparatus and a mold apparatus. The injection apparatus is constructed such that resin heated and melted in a heating cylinder is injected from an injection nozzle. The injected resin is charged into a cavity of the mold apparatus. The molten resin is then cooled and solidified, and the mold apparatus is opened so as to permit removal of a molded article from the mold apparatus.
FIG. 1
is a conceptual diagram of a conventional injection molding machine, and
FIG. 2
is a nozzle touch characteristic chart of the conventional injection molding machine. In
FIG. 2
, the horizontal axis represents an amount of deformation x, and the vertical axis represents a nozzle touch force f.
In
FIG. 1
, numeral
10
denotes an injection apparatus, numeral
11
denotes a heating cylinder, and numeral
13
denotes an injection nozzle provided at the front end (the left end in
FIG. 1
) of the heating cylinder
11
. An unillustrated screw is disposed within the heating cylinder
11
such that the screw can be rotated and can be advanced and retracted by a drive section
12
.
The screw extends rearwardly (rightward in
FIG. 1
) within the heating cylinder
11
, and the rear end (the right end in
FIG. 1
) of the screw is connected to the drive section
12
. The screw has a screw head at the front end thereof and a spiral flute formed on the peripheral surface of a metering portion of the screw, so that the flute defines a groove.
In the injection apparatus
10
having the above-described structure, during a metering stage, the drive section
12
is driven in order to retract the screw (rightward in FIG.
1
), while rotating the screw in a forward direction. Consequently, pellet-shaped resin within an unillustrated hopper flows into the heating cylinder
11
, and is caused to advance (move leftward in
FIG. 1
) along the groove of the screw. At this time, the resin is heated and melted by an unillustrated heater and accumulated on the front side of the screw head.
Further, during an injection stage, the drive section
12
is driven in order to advance the screw, so that the resin accumulated at the front side of the screw head is injected from the injection nozzle
13
and is charged into an unillustrated cavity of a mold apparatus
14
. The mold apparatus
14
is composed of a stationary mold
15
and a movable mold
16
. The movable mold
16
is advanced and retracted by an unillustrated mold clamping apparatus in order to bring the movable mold
16
into contact with the stationary mold
15
and separate the movable mold
16
from the stationary mold
15
. Thus, mold closing, mold clamping, and mold opening are performed.
Subsequently, when the charging of resin into the cavity is completed, cooling water is caused to flow through an unillustrated cooling passage formed within the molding apparatus
14
, so that the resin is cooled. After the resin is solidified, the molding apparatus is opened so as to permit removal of a molded product.
In the injection molding machine, resin may leak from a clearance between the injection nozzle
13
and the stationary mold
15
while the resin is being charge into the cavity, unless the injection nozzle
13
is in contact with the stationary mold
15
with a predetermined pressing force or nozzle touch force.
In order to solve the above-described drawback, a nozzle touch apparatus is provided. The nozzle touch apparatus advances the injection apparatus
10
such that the injection nozzle
13
comes in contact with the stationary mold
15
with a predetermined nozzle touch force. Thus, a nozzle touch operation is completed.
In order to perform the nozzle touch operation, a support member
22
and a motor
25
serving as drive means are fixed to a frame
21
of the injection molding machine; a ball screw shaft
23
is rotatably supported by the support member
22
; and a ball nut
24
is in screw-engagement with the ball screw shaft
23
. Further, the ball screw shaft
23
is connected to an output shaft
25
a
of the motor
25
, and the ball nut
24
is connected to the injection apparatus
10
via a spring
26
. A sensor
28
is disposed to face the spring
26
. The sensor
28
senses a displacement of a certain portion of the spring
26
due to deformation of the spring
26
(hereinafter referred to as a “deforming position”) to thereby detect an amount of deformation.
In this case, when the ball screw shaft
23
is rotated through drive of the motor
25
, the ball nut
24
is advanced from a retracted position, so that the injection apparatus
10
is advanced. Thus, the injection apparatus
10
reaches a nozzle touch position, and the injection nozzle
13
comes into contact with the stationary mold
15
. Subsequently, when the motor
25
is further driven in a state in which the injection nozzle
13
is in contact with the stationary mold
15
, the ball nut
24
is advanced against the urging force of the spring
26
, so that the spring
26
contracts by an amount corresponding to the distance advanced by the ball nut
24
. At this time, the injection nozzle
13
presses the stationary mold
15
with a force corresponding to the amount of deformation of the spring
26
. When the deformation amount of the spring
26
is represented by x, and a pressing force that the injection nozzle
13
exerts on the stationary mold
15
or a nozzle touch force is represented by f, a relationship as shown in
FIG. 2
exists between the deformation amount x and the nozzle touch force f. Accordingly, the nozzle touch force f can be detected through detection of the deforming position of the spring
26
. When the deformation amount x reaches a preset value x
1
and thus a proper nozzle touch force f equal to a target nozzle touch force f
1
is generated, the motor
25
is stopped.
In the nozzle touch apparatus of the conventional injection molding machine, the injection apparatus
10
is connected to the ball nut
24
via the spring
26
. Therefore, if an external force is applied to the injection apparatus
10
due to impact caused by, for example, closing or opening of the molding apparatus
14
or injection of resin, the spring
26
is expanded or contracted, so that the deformation amount x varies.
Therefore, even when the ball nut
24
is accurately positioned, the sensor
28
may erroneously detect the deformation amount x due to expansion or contraction of the spring
26
caused by an external force. In this case, the nozzle touch force f is not accurately detected, with the result that a proper nozzle touch force f equal to the target nozzle touch force f
1
cannot be generated. For example, when the spring
26
is contracted, the nozzle touch force f becomes excessively large, resulting in breakage of the mold apparatus
14
and/or nozzle
13
. When the spring
26
is expanded, the nozzle touch force f becomes excessively small, resulting in resin leaking from the clearance between the injection nozzle
13
and the stationary mold
15
.
Since the spring
26
and the sensor
28
are attached to the injection apparatus
10
, the spring
26
and the sensor
28
are accommodated within an unillustrated casing of the injection apparatus
10
, which deteriorates ease of maintenance and management of the injection molding machine.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above-mentioned problems in the conventional nozzle touch apparatus for an injection molding machine, to provide a nozzle touch apparatus for an injection molding machine which can accurately detect nozzle touch force, which can generate a proper nozzle touch force, and/or which facilitates work for maintenance and management of the injection molding machine.
A nozzle touch apparatus for an injection molding machine according to one example of the present invention comprises: a frame; an injection apparatus having an injec
Arent Fox Kintner Plotkin & Kahn
Heitbrink Jill L.
Sumitomo Heavy Industrie's, Ltd.
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