Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Molding pressure control means responsive to pressure at...
Reexamination Certificate
2001-01-29
2003-07-22
Mackey, James P. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Molding pressure control means responsive to pressure at...
C425S169000, C425S593000
Reexamination Certificate
active
06595766
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a die clamping apparatus having a toggle type clamping mechanism applied to a molding machine such as a die casting machine or an injection molding machine.
Also, the present invention relates to a die clamping force measurement method in a die clamping apparatus capable of correctly measuring the die clamping force.
Further, the present invention relates to a die clamping force adjusting method of a die clamping apparatus capable of correctly adjusting the die clamping force.
2. Description of the Related Art
In the die clamping apparatus of for example a die casting machine, a die clamping force of a pair of dies compatible with the injection pressure of molten metal at the time of injection is required. The die clamping apparatuses are roughly classified into direct pressure type die clamping apparatuses directly pressing against a movable die and toggle type die clamping apparatuses pressing against the same via a toggle mechanism.
In a toggle type die clamping apparatus, there is a self lock mechanism of the toggle mechanism, so there are various advantages such as saving of energy in comparison with a direct pressure type die clamping apparatus.
Here, an example of the configuration of a toggle type die clamping apparatus will be explained by referring to
FIG. 1
to FIG.
4
.
FIG. 1
is a longitudinal sectional view of the configuration of a toggle type die clamping apparatus. The upper half from the center line CL shows the state before the start of closing the die, while the lower half shows the state of completion of closing of the die. Further,
FIG. 2
is a side view of the die clamping apparatus shown in FIG.
1
.
In FIG.
1
and
FIG. 2
, a die clamping apparatus
200
is provided with a pair of dies
4
comprising a fixed die
4
b
and a movable die
4
a,
a link housing
1
, a fixed die plate
2
with the fixed die
4
b
attached thereto, a movable die plate
3
with the movable die
4
a
attached thereto, a base
5
, a toggle mechanism
6
, a crosshead
7
, a hydraulic cylinder
8
, a piston rod
9
, a guide rod
10
, and tie bars
11
.
The die clamping apparatus
200
is provided with an upper and lower pair of toggle mechanisms
6
comprising three links
6
a,
6
b,
and
6
c
between the movable die plate
3
and the link housing
1
.
The fixed die plate
2
is fixed to the base
5
, and the link housing
1
and the movable die plate
3
are provided movably on the base
5
.
The link housing
1
and the movable die plate
3
are connected by tie bars
11
as shown in FIG.
2
. Usually, four tie bars
11
are provided.
The link
6
c
of the toggle mechanism
6
is pivotally connected to the crosshead
7
, the hydraulic cylinder
8
is mounted at substantially the center portion of an outer end face of the link housing
1
, and a front end of the piston rod
9
of this hydraulic cylinder
8
is connected to the crosshead
7
.
The crosshead
7
is movably guided to the guide rod
10
. This crosshead
7
moves along the guide rod
10
in accordance with the movement of the piston rod
9
.
As shown in
FIG. 2
, when the piston rod
9
of the hydraulic cylinder
8
is advanced from a state where the links
6
a,
6
b,
and
6
c
of the toggle mechanism
6
are folded and the links
6
a,
6
b,
and
6
c
are extended, the movable die plate
3
moves toward the fixed die plate
2
and, as shown in
FIG. 3
, the movable die
4
a
contacts the fixed die
4
b.
In the state shown in
FIG. 3
, the links
6
a,
6
b,
and
6
c
of the toggle mechanism
6
are not completely extended, and no die clamping force is generated between the movable die
4
a
and the fixed die
4
b.
Further, a distance H
0
between the movable die plate
3
and the fixed die plate
2
in the state where the movable die
4
a
and the fixed die
4
b
contact and the die clamping force has not been generated between them is referred to as the die height.
When the piston rod
9
is further advanced from this state, the links
6
a,
6
b,
and
6
c
of the toggle mechanism
6
become in almost straight alignment as shown in FIG.
4
and self lock. Further, by the extension of the toggle mechanism
6
, the tie bars
11
connecting the link housing
1
and the fixed die plate
2
are stretched due to elastic deformation, a die clamping force in accordance with the amount of deformation of the tie bars
11
is generated between the movable die
4
a
and the fixed die
4
b,
and the link housing
1
moves on the base
5
with an amount of movement in accordance with the amount of deformation of the tie bars
11
.
When the die height H
0
is changed by the adjustment of the die clamping force or by a change of the die
4
in the die clamping apparatus
200
of the above configuration, the position relative to the fixed die plate
2
is adjusted by the link housing
1
.
As the position adjustment device for adjusting the position of the link housing
1
, for example a spur gear type position adjustment device or a chain type or worm gear type position adjustment device are known. Such a position adjustment device is built in the link housing
1
. The position adjustment device basically is comprised of tie bar nuts screwed with the four tie bars
11
. By controlling the rotation of these tie bar nuts in synchronization, the link housing
1
can be moved along the tie bars
11
.
In the measurement of the die clamping force in the toggle type die clamping apparatus
200
having the above configuration, as disclosed in for example Japanese Examined Patent Publication (Kokoku) No. 5-74770, the method of embedding electric load meters in ends of the tie bars
11
at the link housing
1
side, directly detecting the amounts of deformation of the tie bars
11
at the time of clamping by the electric type load meters, and finding the die clamping force based on the amounts of deformation was employed.
With this method, however, there were the disadvantages that the cost of the electric load meters was high, the work for attachment of the electric load meters was troublesome, the cost of manufacture rose, maintenance of the detection precision was difficult, etc.
In order to overcome such disadvantages, a method of not directly measuring the amounts of deformation of the tie bars
11
, but detecting the amount of movement of the link housing
1
relative to the base
5
when it shifts from a die open state as shown in
FIG. 1
to a die closed state shown in FIG.
4
and calculating the die clamping force based on this amount of movement is disclosed in for example Japanese Examined Patent Publication (Kokoku) No. 5-36219. Namely, the die clamping force is calculated by regarding the amount of movement of the link housing
1
when it shifts from the die open state to the die closed state as the amount of deformation of the tie bars
11
.
However, the position adjustment device is interposed between the link housing
1
and the tie bars
11
. If mechanical error such as backlash exists between the tie bars
11
and the tie bar nuts screwed to them in this position adjustment device, the amount of the mechanical error is contained in the detected amount of movement of the link housing
1
, so the amount of movement of the link housing
1
when it shifts from the die open state to the die closed state and the amounts of deformation of the tie bars
11
may not correctly coincide. For this reason, in the above method, the correct measurement of the die clamping force was difficult. Particularly, it was easily influenced by the backlash between the tie bar and the tie bar nut after adjusting the position of the link housing
1
by the position adjustment device so as to adjust the die clamping force and change the die height H
0
by the change of the dies
4
, so the die clamping force could not be correctly measured.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a die clamping apparatus capable of correctly measuring a die clamping force without use of sensors such as load meters for directly detecting the
Mackey James P.
Pillsbury & Winthrop LLP
Toshiba Kikai Kabushiki Kaisha
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