Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Mold motion or position control
Reexamination Certificate
2000-10-23
2003-05-13
Mackey, James P. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Mold motion or position control
C425S451700, C425S589000
Reexamination Certificate
active
06561785
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a molding clamping apparatus, and more particularly to such a molding clamping apparatus which includes a ballscrew shaft and a ballscrew nut, for moving a movable plate relative to a stationary plate, so as to open, close and clamp a mold consisting of movable and stationary mold halves that are to be fixed to the movable and stationary plates, respectively.
2. Discussion of Related Art
As an apparatus for clamping a mold used for an injection molding machine, a press forming machine or other forming machine, for example, there is known a mold clamping apparatus equipped with a hydraulic cylinder which directly transmits a driving force to the movable plate, or which indirectly transmits the driving force to the movable plate through a toggle link mechanism. There is also known a mold clamping apparatus equipped with a pair or pairs of ballscrew shaft and ballscrew nut which serves to convert a rotational driving force to a reciprocal driving force and then transmit the reciprocal driving force to the movable plate.
As examples of the mold clamping apparatus equipped with the ballscrew shafts and nuts, JP-Y2-01-36587 and JP-Y2-01-36588 disclose apparatuses, in each of which four tie bars are provided to extend between the stationary and movable plates and have respective external threads formed in their outer circumferential surfaces, so as to serve the ballscrew shafts. The external threads of the four tie bars engage respective four internally-threaded ballscrew nuts which are attached to the movable plate. In the apparatus disclosed in JP-Y2-01-36587, the four tie bar are adapted to be rotatable about their respective axes in the forward and reverse directions, while the four ballscrew nuts are fixed to the movable plate so as to be not rotatable relative to the movable plate, so that the four ballscrew nuts are axially moved with rotations of the four tie bars which are driven by an electric motor, whereby the movable plate carried by the four ballscrew nuts are moved toward and away from the stationary plate. In the apparatus disclosed in JP-Y2-01-36588, the four ballscrew nuts are supported by the movable plate rotatably relative to the movable plate, and are driven by an electric motor so as to be rotated, so that the four ballscrew nuts are axially moved, whereby the movable plate carried by the four ballscrew nuts are moved toward and away from the stationary plate.
Owing to the construction in which the four tie bars extending between the movable and stationary plates serve as the ballscrew shafts, each of the above-described apparatuses advantageously has smaller total length and size than those of an apparatus in which the ballscrew shafts are disposed in one of opposite sides of the movable plate remote from the stationary plate. However, the above-described apparatuses, in which the rotational driving force generated by the electric motor is transmitted to the tie bars or the ballscrew nuts through gears, suffer from the problem that the gears meshing with each other generate large noises. This problem of the noises might be somewhat resolved by employing a timing belts or other belts in place of the gears. However, the belts produces particles or dusts as the belts are worn, and the produced particles or dusts problematically contaminate the formed product and the environment.
In the apparatus disclosed in JP-Y2-01-36588, each tie bar is fixed, at one of axially opposite end portions thereof remote from the stationary plate, to an end plate (designated by the reference numeral
14
in
FIG. 1
of the publication) which is disposed movably in the axial direction of the tie bars, so that the end plate is moved when the tie bars are elongated by a reaction force of a mold clamping force (compressive force) which is generated by and between the movable and stationary plates in an operation for closing the mold. That is, the end plate is displaced by a distance corresponding to an amount of the elongation of the tie bars, whereby the servo motor is protected from application of an excessively large load thereto due to the elongation of the tie bars, or whereby a load applied to the servo motor is reduced when the tie bar is elongated. However, the arrangement enabling the displacement of the end plate requires a complicated structure, thereby inevitably complicating even the construction of the entirety of the apparatus.
In view of the above-described problems, the present applicant has proposed a mold clamping apparatus in Japanese Patent Application No. 11-211600. In the proposed apparatus, each of the ballscrew shafts is fixed at an axial end portion thereof to the movable plate, and extends from the movable plate toward the stationary plate so as to pass through the stationary plate, such that the other axial end portion of each ballscrew shaft projects from one of opposite side faces of the stationary plate remote from the movable plate, over a predetermined distance. The servo motors are fixed to the corresponding portions of the one of the opposite side faces of the stationary plate, from which the other axial end portion of each ballscrew shaft projects. Each ballscrew shaft engages, at the other axial end portion projecting from stationary plate, the corresponding one of the ballscrew nuts which are directly fixed to the rotors of the respective servo motors.
This proposed mold clamping apparatus, in which the ballscrew nuts are fixed directly to the rotors of the respective servo motors, no longer suffers from the above-described problem encountered in the conventional apparatus in which the rotational driving force generated by the servo motor is transmitted to the ballscrew shafts and nuts via the gears or belts. That is, the proposed mold clamping apparatus suffers from neither noises generated by the mutually meshing gears, nor dusts produced due to wear of the belts.
However, in the proposed mold clamping apparatus, in which the ballscrew nuts are fixed to the rotors of the respective servo motors so as to be rotated together with the rotors, a relatively large rotational inertia acts on each servo motor, and an accordingly large load is applied to each servo motor, for example, upon initiation and termination of rotation of the servo motor, thereby causing some delay of each change in the momentum of the movable plate during an operation for opening and closing the mold, and increasing a time required for actual initiation or termination of the motion of the movable plate in response to a command inputted by the operator for initiating or terminating the motion of the movable plate. In this respect, the proposed mold clamping apparatus has a difficulty in performing an operation in which the product is required to be formed in a short time.
Further, in the proposed mold clamping apparatus, the servo motors are attached to the one of opposite side faces of the stationary plate remote from the movable plate, and the ballscrew shafts extends from the movable plate toward the stationary plate so as to pass through the stationary plate, as described above. In this arrangement, the above-described other axial end portion of each ballscrew shaft further projects from the stationary plate in a direction away from the movable plate, as the movable plate is moved toward the stationary plate. This arrangement deteriorates the condition of the operator's operation, reducing the efficiency of the operation. For example, where this mold clamping apparatus is used for an injection molding machine, the projecting axially end portions of the ballscrew shafts, as well as the servo motors attached to the side face of the stationary plate, disturb various operations which should be carried out on the side of the stationary plate remote from the movable plate, such as an operation for removing a purging resin from a nozzle of the injection molding machine which is located on the side of the stationary plate remote from the movable plate.
Thus, even the apparatuses havi
Morita Ryozo
Oka Keijiro
Shinoda Takashi
Burr & Brown
Kabushiki Kaisha Meiki Seisakusho
Mackey James P.
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