Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
2002-06-25
2004-10-19
Mackey, James P. (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
C425S169000, C425S190000, C425S214000, C425S451700, C425S589000, C425S595000
Reexamination Certificate
active
06805827
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a clamping device. More particularly, the present invention relates to a hybrid type clamping device in which a hydraulic drive system used for a large clamping device and an electric drive system used for a small clamping device are combined with each other. Further, the present invention relates to a method of increasing and decreasing hydraulic pressure used in this clamping device. Furthermore, the present invention relates to a method of releasing a mold.
BACKGROUND ART OF THE INVENTION
Conventionally, main stream clamping devices used for injection molding machines or die casting machines are hydraulic drive systems such as direct pressure type clamping devices or toggle type clamping devices. Recently, in order to meet the demand of saving energy and making the working environment clean, an electric drive type clamping device, in which a mold can be opened and closed when a rotary motion of a servo motor is converted into a linear motion of the mold by a ball screw nut, has been widely used, especially in the field of small molding machines.
However, although this small clamping device in which the electric drive system is used can meet the demand of saving energy and making the working environment clean, when the size of this small clamping device is proportionally increased so that the electric drive system can be applied to a large clamping device, the size of the clamping device cannot be increased very much because an increase in the size of a servo motor, and of a ball screw, are restricted. In order to solve the above problems, a hybrid type clamping device, in which an electric drive system is used for a mold opening and closing means and a hydraulic system is used for a clamping force generating means, has been devised.
For example, Japanese Unexamined Patent Publication No. 6-246806 discloses an example of the hybrid type clamping device in which a metallic mold is opened and closed when a movable platen is moved by a screwing motion of a male screw conducted by an AC servo motor, and a clamping motion conducted after the mold has been closed is conducted by a hydraulic means. This hydraulic clamping device is composed as follows. At the back of the movable platen, a hydraulic operating board is arranged which includes a closed chamber having a tightly closed bladder into which hydraulic fluid is charged. After the hydraulic operating board has been locked together with a movable platen, the male screw member is further moved by an electric motor. Due to the foregoing, the tightly closed bladder is pressurized, so that a clamping force is given to a metallic mold by a piston and via the movable platen. In the case of opening the metallic mold, the male screw member is reversed so that the movable platen can be drawn in.
In the conventional hybrid type clamping device described above, while the tightly closed bladder is being pressurized by the male screw in the closed chamber, the pressurizing action is maintained when the male screw member is screwed by an AC servo motor by a ball screw mechanism. Further, both the mold releasing and the mold opening are conducted when the male screw member is screwed in the same manner. Therefore, in the working time when the mold is opened and closed and when the clamping force is given to the mold and when the mold is released, a load must be always given to the electric motor which is a drive source. Therefore, it is impossible to sufficiently accomplish energy saving. Further, since both the electric drive system and the hydraulic drive system are jointly used, the structure of the clamping device becomes complicated, and the frequency of mechanical breakdown is increased.
The above conventional hybrid type clamping device is composed in such a manner that the tightly closed bladder is pressurized by the male screw in the closed chamber. Therefore, unless air is completely removed from the tightly closed bladder when the tightly closed bladder is charged with hydraulic fluid, the clamping force cannot be appropriately given to the mold. It is very difficult to form the tightly closed bladder into which hydraulic fluid is charged in accordance with a volume of the stationary closed chamber. Further, as the tightly closed bladder is deformed into a recessed shape, there is a possibility that the bladder is damaged and the hydraulic fluid leaks out from the bladder. Therefore, it is impossible to increase the clamping force.
Further, the clamping device used for a conventional injection molding machine or die casting machine is composed in such a manner that a stationary platen and a movable platen, to which metallic molds are respectively attached, which are connected with each other by tie rods, are fixed to each other at a mold closing position by a platen lock means. Usually, the platen lock means is composed of a pair of split nuts capable of being opened and closed. When the pair of split nuts are engaged with ring grooves or screw grooves, the movable platen can be fixed and held at the mold clamping position.
In this connection, when a metallic mold is changed, the thickness (die-height) of the metallic mold is changed. Therefore, the mold closing position is naturally changed, and the lock position of the movable platen is also changed. When the die-height is changed as described above, the pitch of engagement of a split nut with a tie rod is shifted in some cases. Accordingly, there is usually provided a die-height adjusting mechanism.
As a conventionally well known die-height adjusting mechanism, as disclosed in Japanese Examined Patent Publication No. 44-16008, there is provided a mechanism in which tie rods are arranged so that they can be moved in the axial direction with respect to a stationary platen so that a phase shift caused between a split nut and the tie rod can be adjusted. Further, as disclosed in Japanese Unexamined Patent Publication No. 11-235741, there is provided a mechanism in which a clamping cylinder is fixed onto a mount moving when a mold is opened and closed, and a movable platen capable of moving on this mount is connected to the clamping cylinder, and when a phase shift is caused between a split nut and a tie rod at a mold closing position, a distance between the clamping cylinder and the movable platen is adjusted so that the die-height can be adjusted.
However, the former mechanism is disadvantageous in that the tie rod must be made movable with respect to the stationary platen, so that the size of the device is increased and the clamping accuracy is deteriorated. The latter mechanism is disadvantageous in that a large-scale device is required for adjusting the die-height. Further, it is necessary to compose the device in such a manner that while the clamping cylinder is being moved together with the movable platen, the distance between them must be made variable.
In the case of a booster-ram type clamping device, the mold opening is conducted in a front hydraulic chamber of the clamping cylinder. Therefore, the accuracy of the entire inner face of the clamping cylinder must be high, and further the diameter is extended. Accordingly, it is hard to conduct precision machining, which results in increasing the manufacturing cost. In the case where the clamping cylinder, the diameter of which is large, is used for opening the mold as described above, the total length of a die casting machine or an injection molding machine is extended, and it becomes difficult to install the die casting machine or the injection molding machine in a small space.
In order to solve the above problems, Japanese Unexamined Patent Publication No. 10-94864 discloses the following arrangement. As shown in
FIGS. 31 and 32
, the metallic mold attaching plate
3
is put and held on the stationary platen
2
, at a plurality of corners of which the tie rods
1
are provided, and the cylinder holes
4
open to the metallic mold attaching plate
3
side are formed on the stationary platen
2
. Further, there are provided rams
5
which are slidably engag
Kami Masahiro
Kamota Iseo
Kubozoe Kazuo
Okada Tokuhisa
Ono Hidenobu
Mackey James P.
Piper Rudnick LLP
Ube Machinery Corporation, Ltd.
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