Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With product ejector
Reexamination Certificate
2000-05-11
2002-08-27
Mackey, James P. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With product ejector
C264S039000, C264S040500, C425S590000, C425S595000
Reexamination Certificate
active
06439875
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to mold clamping apparatus of an injection molding machine which includes a driving device having a ball-screw driven by an electric motor by which a movable platen is reciprocally moved toward and away from a stationary platen, whereby a mold is accordingly closed and opened. More particularly, the present invention is concerned with a mold clamping apparatus having a novel structure wherein a hydraulic cylinder-piston mechanism is utilized to obtain an increased mold clamping force, and an effective method for controlling operation of the mold clamping apparatus.
2. Description of the Related Art
As a device for clamping a mold used for an injection molding machine, for example, there are known a direct-pressure type mold clamping device having a hydraulic cylinder-piston mechanism which generate a driving force directly applied to a movable platen so as to move the movable platen toward and away from a stationary platen for opening and closing the mold defined therebetween and so as to force the movable platen to the stationary platen for clamping the mold therebetween, and a toggle-type clamping device having a link mechanism in which the driving force is applied to the movable platen via the link mechanism. Another type of mold clamping device is also known, that device includes a ball-screw and an electric motor. In this ball-screw type clamping device, a rotational driving force of the electric motor is converted into a reciprocal driving force by the ball-screw, thereby executing the above-indicated mold opening and closing and clamping action, by utilizing this reciprocal driving force.
In the mold opening and closing actions, such a mold clamping device as described above is required to move the movable platen at a relatively-high velocity, in order to shorten a cycle time of a forming operation of the injection molding machine. In the mold clamping action, on the other hand, the mold clamping device is required to apply a relatively large driving force to the movable platen so that the movable platen is forced toward the stationary platen with a sufficiently large mold clamping force, thereby assuring a high accuracy of the injection molding. However, the conventional mold clamping device using the ball-screw suffers from difficulty in meeting both of these requirements.
The present inventor has been proposed in JP-U-3-3389 (publication number 3-3389 of Japanese Utility model application) a mold clamping device having an electric motor and a ball-screw, as well as a hydraulic cylinder-piston mechanism. This mold clamping device further includes an accumulator for accumulating a pressurized fluid, and is arranged such that the movable platen is moved by using the ball-screw for opening and closing the mold and is forced toward the stationary plate for clamping the mold therebetween by means of the hydraulic cylinder-piston mechanism and by utilizing the pressurized fluid accumulated in the accumulator during opening and closing the mold by using the ball-screw. This mold clamping device makes it possible to meet both of the above-indicated requirements. Namely, the proposed mold clamping device permits the mold opening and closing operation at a relatively-high velocity by using a combination of the electric motor and a small-sized ball-screw, and assures the generation of the relatively large mold clamping force with ease by utilizing the hydraulic cylinder-piston mechanism.
However, the proposed mold clamping device utilizes the pressurized fluid previously accumulated in the accumulator and then applied to a cylinder chamber of the cylinder-piston mechanism via a suitable switch valve. This requires the switching operation of the switch valve under a given hydraulic pressure generated by the pressurized fluid, needing a relatively large-sized switch valve and a relatively-large driving force for driving the large-sized switch valve, resulting in a time-consumed switching operation of the switch valve. In addition, the proposed mold clamping device suffers from a problem of pressure losses of the pressurized fluid during accumulated in the accumulator. Therefore, the proposed mold clamping device possibly suffers from insufficiency of the required characteristics.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide an improved mold clamping apparatus which is capable of generating a desired driving force with ease by means of an electric motor and a ball-screw, for assuring a reciprocal movement of a movable platen at a relatively-high velocity, and generating a relatively-large mold clamping force with ease by using a hydraulic device.
It is a second object of the present invention to provide a suitable method for controlling an operation of such a mold clamping device.
The first object of the present invention may be achieved according to a first aspect of this invention, which provides a mold clamping apparatus of an injection-molding machine for clamping a mold consisting of a stationary mold half and a movable mold half, said mold clamping apparatus comprising: (a) a stationary platens fixedly disposed on a base of the injection-molding machine and being fixed with the stationary mold half; (b) a rear platen fixedly disposed on the base of the injection-molding machine and being opposite to and spaced apart from the stationary platen and; (c) a movable platen movably disposed between the stationary and rear platens and being fixed with the movable mold half; (d) an electrically-operated movable-platen-driving device of ball-screw type, including a first ball-screw shaft supported by one of the movable and rear platens, a first ball-nut threaded-engaged with the first ball-screw shaft and supported by the other of the movable and rear platens, and a movable-platen-driving-electric motor adapted to rotate the first ball-screw shaft and nut relative to each other so as to generate a relative longitudinal motion of the first ball-screw shaft and nut so that the movable platen is moved toward and away from the stationary platen to close and open the mold; (e) a pressure-generating cylinder device disposed on the rear platen and having a pressure-generating piston being moved by the relative longitudinal motion of the first ball-screw shaft and nut in order to generate a hydraulic pressure; (f) a mold clamping cylinder device disposed on the rear platen and adapted to generate a mold clamping force based on the hydraulic pressure generated in and applied from the pressure-generating cylinder device, the mold clamping cylinder device having a mold clamping ram which is connectable to the movable platen for applying the mold clamping force to the movable platen; and (g) an engaging device having a first operating position for connecting the mold clamping ram with the movable platen, and a second operating position for disconnecting the mold clamping ram from the movable platen, the mold clamping apparatus clamping the mold such that the movable platen is moved toward the stationary platen to close the mold therebetween, and the pressure-generating cylinder is operated to generate the hydraulic pressure, based on the relative longitudinal motion of the first ball-screw shaft and nut, while the engaging device is placed in the first operating position in order to apply the mold clamping force generated in the mold clamping cylinder device to the movable platen.
In the mold clamping apparatus constructed according to the first aspect of the present invention, the mold opening and closing operation is performed such that the ball-screw type movable-platen-driving device is used for reciprocally moving the movable platen between a mold opening position and a mold closing position of the movable platen. Namely, the first ball-screw shaft and the first ball-nut of the movable-platen-driving device are rotated relative to each other by the movable-platen-driving-electric motor of the movable-platen-driving device. This ball-screw mechanism is
Morita Ryozo
Oka Keijiro
Shinoda Takashi
Takashi Ryoji
Tomita Satoshi
Kabushiki Kaisya Meiki Seisakusyo
Mackey James P.
Oliff & Berridg,e PLC
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