Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – Mold having movable core or movable pin
Reexamination Certificate
2000-05-31
2002-05-28
Mackey, James P. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
Mold having movable core or movable pin
C425S590000, C425S595000
Reexamination Certificate
active
06394787
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mold clamping apparatus, and more particularly, to a mold clamping apparatus having a movable core for use in injection molding for making molded products such as preforms, which clamping apparatus includes hydraulic circuits that enable reduced operating time in which molds are opened and closed.
2. Description of the Prior Art
The mold clamping apparatus of the type having a stationary mold to form a body of molded products, a movable mold which closes with respect to the stationary mold to form an opening in molded products, and a core which is placed in the stationary mold through the movable mold and is movable into and out of the stationary mold includes those employed in rotary type injection machines disclosed in the publication of Japanese Patent No. 2, 832, 263 which is incorporated herein by reference. In such a mold clamping apparatus, a mold opening/closing cylinder effects opening and closing of the movable mold, and the movement of the core into and out of the stationary mold is effected by a differential mold clamping cylinder, which is separate from the mold opening/closing cylinder and is fitted with a booster ram.
Referring to FIGS.
1
(A) and
1
(B), the above-described conventional clamp apparatus is shown having a machine bed
1
, a movable platen
2
, a pair of tie bars
3
,
3
, a pair of mold opening/closing cylinders
4
,
4
, and a differential mold clamping cylinder
6
. The tie bars
3
,
3
are vertically mounted on the machine bed
1
and penetrate through the opposite ends of the movable platen
2
which is movable upward and downward. The mold clamping cylinders
4
,
4
are arranged between the movable platen
2
and the machine bed
1
and cause the movable platen
2
to move upward and downward as a piston
41
in each of the cylinders moves upward and downward. Arranged on the upper ends of the tie bars
3
,
3
is the differential mold clamping cylinder
6
which accommodates a mold clamping ram
5
. The mold clamping ram
5
, which is arranged above the movable platen
2
, is directed downward.
A mold clamping piston
5
a
is arranged in the differential mold clamping cylinder
6
. The inside of the cylinder
6
has a relatively larger inner diameter than the outer diameter of the piston
5
a
in the area above the mold clamping position, such that the piston
5
a
contacts the inner surface of the cylinder only in the lower-most region of the cylinder to effect mold clamping. This leaves a communication gap about the piston
5
a
in the upper region of the cylinder. A booster ram
7
is inserted into the above-described mold clamping ram
5
from the upper end of the mold clamping ram. Arranged on the sides of the cylinder
6
are a bypass
8
which connects the upper region of the cylinder
6
to the lower region thereof and a pair of charge cylinders
9
,
9
which communicate with the cylinder
6
at the lower end thereof. Pistons
10
,
10
are arranged in the charge cylinders
9
,
9
, respectively. Also, arranged above the movable platen
2
is a mold clamping platen
11
through which the tie bars
3
,
3
are arranged. The pistons
10
,
10
as well as the mold clamping ram
5
are connected to the upper surface of the mold clamping platen
11
.
In such a mold clamping apparatus, a stationary mold
12
to form a body of the molded products such as preforms is placed on the upper surface of the machine bed
1
, and a movable mold
13
to form an opening in the molded products is fixed to the lower surface of the movable platen
2
. Also, a core
14
to define an inner space in a preform is arranged on the lower surface of the mold clamping platen
11
such that it can move through the movable mold
13
into and out of a cavity defined inside the stationary mold
12
.
Opening of the movable mold
13
with respect to the stationary mold
12
is effected by supplying hydraulic oil to a mold opening oil chamber
42
which is defined by a piston
41
in the lower region of the mold opening/closing cylinder
4
, while closing of the movable mold
13
with respect to the stationary mold
12
is effected by supplying hydraulic oil to a mold closing oil chamber
43
which is defined in the upper region of the mold opening/closing cylinder
4
.
Opening of the core
14
is effected by supplying hydraulic oil from the booster ram
7
to the mold clamping ram
5
. Closing and clamping of the core
14
are effected by supplying hydraulic oil to the differential mold clamping cylinder
6
. When inside of the differential mold clamping cylinder
6
is pressurized, the mold clamping piston
5
a
is pushed downward due to the difference in area between the upper surface and the lower surface of the piston to which the pressure applies. This in turn moves the mold clamping ram
5
downward. Upon this, the hydraulic oil that is present below the mold clamping piston
5
a
flows through the communication gap, around the piston, to above the piston. Thus, no hydraulic resistive force is exerted while the mold clamping piston
5
a
is moving downward. After the mold clamping piston
5
a
fits in the lower-most region of the cylinder
6
, however, pressure builds up in the cylinder in the same manner as in a typical mold clamping cylinder. This clamps the molds.
This differential mold clamping cylinder
6
has the characteristics that the high-speed mold closing as well as mold clamping can be effected with a small supply of hydraulic oil. In contrast, in the mold opening/closing cylinder
4
, which is of a typical construction and includes the two oil chambers
42
,
43
defined by the piston
41
, the speed at which the molds are closed and opened is varied depending on the discharge volume of the hydraulic pumps connected to the cylinder. The pump discharge volume needs to be increased in order to make the opening of the mold by the mold opening/closing cylinder
4
faster. Therefore, it has been difficult to shorten the length of the time it takes for the molds to open, or to close, by simultaneously operating the mold opening/closing cylinder
4
and the differential mold clamping cylinder
6
, each of which employs different system.
SUMMARY OF THE INVENTION
The present invention addresses the above-mentioned problem associated with the differential mold clamping cylinder utilized. Accordingly, it is an object of the present invention to provide a novel mold clamping apparatus in which the hydraulic oil forcibly discharged from one of the differential mold clamping cylinder and the mold opening oil chamber of the mold opening/closing cylinder is delivered to the other as their operating oil in an alternating manner, whereby the simultaneous operation of the two kinds of cylinders, which has been regarded as difficult until now, is realized, leading to reduction in the operating time required for the molds to open and close.
According to the present invention, there is provided a mold clamping apparatus comprising a bed on which a stationary mold to form a body of a product to be molded is placed; a pair of tie bars vertically arranged on the bed; a movable platen having each of the tie bars arranged through the opposite ends thereof, and having on its lower surface a movable mold which closes with respect to the stationary mold to form an opening in molded products; a mold opening/closing cylinder arranged between the bed and the movable platen, wherein the mold opening/closing cylinder moves the movable platen upward and downward to effect the opening and closing of the movable mold, wherein the mold opening/closing cylinder includes a mold opening oil chamber and a mold closing oil chamber, each of the oil chambers defined by a piston, and wherein the mold opening/closing cylinder has a hydraulic line for supplying/discharging hydraulic oil to/from each of the oil chambers; a mold clamping platen having a core movable into and out of the stationary mold through the movable platen; and a differential mold clamping cylinder arranged on the upper end of the tie
A. K. Technical Laboratory Inc.
Mackey James P.
Weingarten Schurgin, Gagnebin & Lebovici LLP
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