Plastic article or earthenware shaping or treating: apparatus – Mold opening and closing means and segmented female mold – Rotary cam
Patent
1986-10-21
1988-11-01
Hoag, Willard E.
Plastic article or earthenware shaping or treating: apparatus
Mold opening and closing means and segmented female mold
Rotary cam
72454, 100290, 164303, 164306, 164312, 4254517, B29C 4506, B22D 1726
Patent
active
047815680
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a mold clamping unit of an injection molding machine.
DESCRIPTION OF THE RELATED ART
Mold clamping units of injection molding machines open/close a mold and clamp the mold. Conventional injection molding machines use a hydraulic drive source for driving the mold clamping units. The mold clamping force is generated by extension of a tie-bar between rear and moving platens. Since a hydraulic drive source is used, the mold clamping operation is difficult to control, and the arrangements of the hydraulic unit and the selector valve are complex. In addition, an ejector unit must be provided in the mold clamping section to take up a mold product, and these mold clamping and ejector units must be arranged normally among four tie-bars. When the injection molding machine is large and has a large output, a sufficient space is reserved for these units and no problem occurs. When the injection molding machine is small, however, the space for a mold clamping section is small, and the mount position for the ejector unit and so on is limited.
SUMMARY OF THE INVENTION
It is an object of the present invention to simplify the structure of a mold clamping unit of an injection molding machine and increase a space for a mold clamping section to facilitate mounting of an ejector unit and so on, thus providing a compact mold clamping unit having a small number of components.
In order to achieve the above objects, according to the present invention, a plurality of ball screws are mounted between front and rear platens at equal distances from centers of molds mounted on the front and moving platens and at predetermined angular intervals. Ball nuts mounted on the moving platen are threadedly engaged with the ball screws. A servo motor moves the moving platen along the ball screws through the ball screws and the ball nuts, and opens/closes and clamps the mold. When the mold is to be clamped, the mold clamping force is generated by a stress caused in the ball screws.
In this manner, according to the present invention, a servo motor is used as a drive source for the mold clamping unit. Tie-bars which are conventionally used to generate a mold clamping force are eliminated. The moving platen is moved forward/backward by the servo motor. The ball screws for moving the mold forward/backward are used in place of the tie-bars. A stress generated in the ball screws upon mold clamping is utilized to clamp the mold. Therefore, the structure of the mold clamping unit is simplified, the number of components is decreased, and a large space can be reserved for the mold clamping section, thus facilitating mounting of the ejector unit and so on.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front view of a mold clamping section of an injection molding machine according to a first embodiment of the present invention;
FIG. 2 is a right side view of the mold clamping section shown in FIG. 1; and
FIG. 3 is a front view of a mold clamping section according to a second embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIGS. 1 and 2 show a mold clamping unit of an injection molding machine according to a first embodiment of the present invention. Referring to FIGS. 1 and 2, reference numeral 1 denotes a front platen; and 2, a rear platen. The front and rear platens 1 and 2 are fixed on a base 15 of the injection molding machine. Two guide rods 8 and two ball screws 4 are fixed between the front and rear platens 1 and 2. The guide rods 8 are fixed on the rear platen 2 through bushings 14 so as to be slidable along the axial direction.
As shown in FIGS. 1 and 2, molds 6 and 7 are mounted on the front platen 1 and a moving platen 3 respectively. The two ball screws 4 are arranged to be symmetrical (with an angular interval of 180.degree.) with each other about centers c of contact surfaces 6a and 7a of the molds 6 and 7, and to be spaced apart at equal distances l from each other. The two guide rods 8 are also symmetrical with each other in the same manner as in the case
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Fanuc Ltd.
Hoag Willard E.
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