Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Mold motion or position control
Patent
1989-04-13
1991-12-03
Heitbrink, Timothy
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Mold motion or position control
264 405, 4254514, 4254515, 425589, 425592, B29C 4580
Patent
active
050696130
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a mold clamping apparatus for use in an injection molding machine, and more particularly, to an electrically-operated crank type mold clamping apparatus with a variable stroke, which is provided with a movable platen adjustable in length stroke between a mold-clamping position and a mold-opening position.
BACKGROUND ART
Mold clamping apparatuses of an injection molding machine are classified into toggle, direct, and crank types in relation to a drive force transmission mechanism, and are classified into hydraulic and servomotor-operated types in relation to a drive force generating source.
In general, a hydraulic injection molding machine uses an operating fluid which is liable to be affected by the atmospheric temperature so as to expand and contract in volume. For this reason, a stable clamping force and repeatability are difficult to obtain. Moreover, complicated maintenance is required, and it is difficult to obtain clean molding products. In this respect, an advantage of a servomotor-operated mold clamping apparatus, without the need of using pressurized fluid, has been recognized.
In a servomotor-operated direct mold clamping apparatus, a complicated control is required for adjustment of the mold-opening stroke. It is difficult to produce a large mold clamping force because of the difficulty in changing to any significant degree magnitude of the drive force during the time between when mold-opening or mold-closing is effected and when mold clamping is effected.
A servomotor-operated toggle mold clamping apparatus is capable of producing a large mold clamping force by increasing the motor output by means of a toggle mechanism. Significant labor is required, however, for a lockup operation, and hence a high-speed injection molding cycle cannot be achieved.
On the other hand, a crank mold clamping apparatus is advantageous in that it has a simplified structure and is capable of carrying out the injection molding cycle at a high speed. However, this type of apparatus is arranged so that a moving platen assumes the mold-closing position and the mold-opening position when a crank reaches its top dead center and bottom dead center, respectively, during one revolution of the crank, and hence the mold-opening stroke of the apparatus is fixedly determined in dependence on the crank length. Thus, it is poor in versatility. For instance, when a three plate type of mold, having a stripper plate for ejecting a mold product, disposed for movement between mold halves which are attached to the front and movable platens, respectively, is employed in an injection molding machine having a fixed mold-opening stroke, only a particular mold is usable for a particular injection molding machine because an individual mold has its proper mold-opening distance. Therefore, this type of mold lacks usefulness in practical use unless it is employed in a mold clamping apparatus which is variable in its mold-opening stroke. In this respect, conventionally, the crank mold clamping apparatus having the above-mentioned advantages has been hardly utilized.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a crank mold clamping apparatus with variable stroke, which has an arbitrarily adjustable mold-opening stroke, and hence makes it possible to employ various types of molds.
In order to achieve the above-mentioned object, according to the present invention, a crank mold clamping apparatus for use in an injection molding machine having a movable platen, comprises a crank disposed for rotation, a coupling member coupling the crank and the movable platen, means coupled to the crank for driving the crank in forward and reverse rotation, means for variably setting a mold-opening stroke, and means for controlling the driving means so that the crank is rotated forwardly and reversely within a limited rotational angular region corresponding to the thus set mold-opening stroke.
According to the present invention, since the crank is rotated forwardly and reversely
REFERENCES:
patent: 3830614 (1974-08-01), Kurtz
patent: 4158539 (1197-06-01), Arends et al.
patent: 4588364 (1986-05-01), Schad
patent: 4710119 (1987-12-01), Otake
Inaba Yoshiharu
Kamiguchi Masao
Fanuc Ltd
Heitbrink Timothy
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