Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Mold motion or position control
Patent
1988-04-13
1989-05-09
Woo, Jay H.
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Mold motion or position control
425171, 425590, B29C 4580
Patent
active
048284750
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a direct-pressure type mold clamping apparatus of an injection-molding machine, which is capable of effecting mold-closing and mold-opening at high speed and of producing a required mold clamping force.
2. Description of the Related Art
An injection-molding machine is furnished with a toggle type mold clamping mechanism, in which a drive source and a movable platen are connected by means of a toggle link, or a direct pressure type mold clamping mechanism. The drive source and the movable platen are connected directly so as to open or close and clamp dies that are attached individually to the movable platen and a stationary platen.
In the mold clamping operation, the dies must be clamped with a great force. Thus, a requisite for the drive source of a mold clamping mechanism is the capability of producing a great clamping force. In the process of injection molding, moreover, the time required for the manufacture of each molding, i.e., the cycle time, is expected to be shortened. Another requisite for the drive source, therefore, is to be able to drive the dies at high speed while they are being opened or closed.
The toggle link acts to help the dies open and close at high speed, and to facilitate the production of a great clamping force. Thus, the toggle type mold clamping mechanism fulfills both of the aforesaid requirements. The direct pressure type mold clamping mechanism, on the other hand, has the advantage over the toggle type mold clamping mechanism that it does not require mold thickness adjustment to compensate for changes in die thickness. It is difficult for the direct pressure type mold clamping mechanism, however, to satisfy both the aforementioned requirements. In the case of a direct-pressure type mold clamping mechanism using a motor as its drive source, for example, both those requirements can be fulfilled only if the motor used has a very large capacity, and therefore, is an expensive one. In consequence, the manufacturing cost of the injection-molding machine increases.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a motor operated, direct pressure type mold clamping apparatus which is capable of performing accurate, high speed mold closing and opening operations and of producing a required mold clamping force, without the use of a special large capacity motor.
In order to achieve the above object, a mold clamping apparatus of an injection-molding machine according to the present invention comprises conversion means which includes a rotating member and a rectilinear motion member movable in unison with a movable platen, the conversion means serving to convert a rotary motion of the rotating member into a rectilinear motion of the rectilinear motion member. The mold clamping apparatus further comprises transmission means for transmitting the rotation of a servomotor to the rotating member, and a speed reducer for reducing the rotating speed and increasing the rotatory force or torque of an induction motor, and transmitting the increased rotatory force to the transmission means. The speed reducer and the transmission means are releasably coupled by means of clutch means.
Further, the mold clamping apparatus comprises numerical control means, position detecting means coupled to the servomotor for detecting the moved position of a movable platen, a servo circuit for driving the servomotor, and torque limit means responsive to a torque limit command from the numerical control means for applying torque limit on the servomotor, the servo circuit including an error register for receiving pulse signals from the position detecting means and distributed pulse signals from the numerical control means. The numerical control means is adapted to supply a torque limit command which causes the servomotor to be substantially inoperative. It also actuates the clutch means when the movable platen, driven by means of the servomotor, reaches a first predetermined position in which
Fanuc Ltd.
Heitbrink Timothy W.
Woo Jay H.
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