Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1993-02-10
1994-01-18
Heitbrink, Jill L.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
425135, 425150, 425574, 425592, 425593, B29C 4576
Patent
active
052797783
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a positioning method of moving/pressing means for moving and pressing a movable member of an injection molding machine against a stationary member through drive control by a servomotor.
BACKGROUND ART
Conventionally known are motor-operated injection molding machines which use servomotors for driving a mold clamping mechanism, nozzle touching mechanism, etc.
The motor-operated injection molding machines which utilize a servomotor for the mold clamping mechanism are classified broadly into two categories: a straight-hydraulic type, in which a movable platen fitted with a movable-side mold is linearly moved for mold clamping by driving a ball-nut-and-screw mechanism by means of the servomotor, and a type in which the mold clamping is effected by pushing out the movable platen by means of a link mechanism. In general, the link mechanism of the latter type may be formed of a toggle mechanism or a crank mechanism.
Referring now to the diagrams of FIGS. 4 and 5, the respective operations of mold clamping mechanisms, in which the movable platen is pressed against a stationary platen by means of the link mechanism, will be described. In FIG. 4, which illustrates the operation of a link mechanism using a crank, symbol 1a designates the crank, which is rotated around a support joint Q1 by means of a servomotor M. A driving joint Q2 of the crank 1a is connected to an action joint Q3, on the side of a movable platen mp for use as a movable member through a link 1b. When the crank 1a is rotated in the clockwise direction of FIG. 4 by driving the servomotor M in this arrangement, the movable platen mp linearly moves in the direction of the arrow of FIG. 4 (i.e., toward the stationary platen) to come into contact with the stationary platen, thereby producing a mold clamping force. Thereupon, positioning is effected by commanding the servomotor M to take a position such that the driving joint Q2 is located on a line which connects the support joint Q1 and the action joint Q3, after adjusting the position of the support joint Q1 or the like so that a set mold clamping force is produced in a state (lockup state) such that the support joint Q1, driving joint Q2, and action joint Q3 are situated substantially on a straight line, as indicated by dotted line in FIG. 4. In the state that the set mold clamping force is obtained with the support joint Q1, driving joint Q2, and action joint Q3 arranged on a straight line, as a result, the crank 1a and the link 1b receive a reaction force against the mold clamping force in the lockup state in which they are stretched to their full length and situated on a straight line, so that no rotatory force is applied to the crank 1a. Thus, no external force acts so as to rotate the servomotor.
FIG. 5 is a diagram for illustrating the operation of a mold clamping mechanism using a link mechanism of the (double) toggle type. The principle of operation of this mechanism resembles that of the one using the crank mechanism of FIG. 4.
More specifically, when a ball screw bs is driven by a servomotor M, a toggle head th, which is integral with a nut threadedly engaged with the ball screw bs, linearly moves. As this is done, the movable platen moves toward the stationary platen in a manner such that links 1a and 1b and links 1c and 1d gradually shift their respective postures from bent positions, indicated by full lines in FIG. 5, to stretched positions, indicated by dotted lines. Thereupon, the servomotor is commanded to take a position for a set mold clamping force (position such that a support joint Q1, driving joint Q2, and action joint Q3 are situated on a straight line), after adjusting the position of the support joint Q1 or the like so that the set mold clamping force is produced in a state (lockup state) such that the support joint Q1, driving joint Q2, and action joint Q3 are situated substantially on a straight line, as indicated by each dotted line in FIG. 5. In the state that the set mold clamping force is obtained in this manner, as in
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patent: 5059365 (1991-10-01), Hertzer et al.
patent: 5069613 (1991-12-01), Inaba et al.
patent: 5147659 (1992-09-01), Watanabe et al.
Ito Susumu
Kamiguchi Masao
Kobayashi Minoru
Tai Ryuji
Taira Takayuki
Fanuc Ltd.
Heitbrink Jill L.
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