Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1996-05-21
1998-04-07
Mackey, James P.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
264334, 425139, 425556, B29C 4540
Patent
active
057360790
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an improvement of a method in which a molded product, which remains in a cavity or a core of a mold after being injection-molded by an injection molding machine, is released from the cavity or the core to be dropped outside by protruding an ejector pin to the cavity or the core.
BACKGROUND ART
In a known ejector apparatus, a molded product, which is difficult to be released from a mold, is forcedly released or unmolded from a movable mold by repeatedly executing the protruding motion of an ejector pin. In the conventional ejector apparatus, however, a reciprocating motion in which the ejector pin is protruded from an unmolding start position to a given protrusion completion position and is returned again to the unmold start position is simply repeated. Therefore, the ejector apparatus of this type has a disadvantage such that if the number of repetitions of protruding motion is increased to perform a reliable unmolding operation, the cycle time of the molding operation increases.
Especially when the molded product sticks to the ejector pin itself, it is necessary to repeatedly execute such a protruding motion, resulting in a marked increase in cycle time. In many of the conventional ejector apparatuses, the return position of an ejector rod is set at a position further behind the end face of an ejector plate from which the ejector pin is erected, so that in many instances a delay in motion is often caused by a useless increase in motion stroke of the ejector rod. When the molded product, sticking strongly to the ejector pin, is not removed from the mold by single protruding motion, the ejector pin is strongly pushed out at every protruding motion to give an impact force to the molded product. This gives rise to a problem such that a tear is produced on the molded product or the ejector pin runs through the molded product, producing deformation.
Unexamined Japanese Patent Publication No. 59-42941 discloses an ejector apparatus in which a plurality of cycles of protruding motion are executed in a short period of time by starting the next protruding motion of the ejector pin before completely returning the ejector pin to the unmold start position after the protrusion of the ejector pin has been completed. In the ejector apparatus of this type, only the ejector pin protrusion start position in the second and subsequent cycles of reciprocating motion can be changed, and the ejector pin protrusion completion position is always constant in any cycle of protruding motion. Therefore, this gives rise to a problem such that the unmolding operation according to the unmold property of molded product cannot be performed. Also, a plurality of mechanical detection switches for detecting the position of the ejector pin are arranged to check the return position and the protrusion completion position of the ejector pin, so that the construction of the ejector apparatus becomes complex. Thus, the return position and the protrusion completion position of the ejector pin cannot be changed (the installation positions of the detection switches cannot be changed either) while the protruding motion are repeated continuously. That is to say, as described above, the ejector apparatus invites a problem such that an unmolding operation according to the unmold property of the molded product cannot be performed. Further, a reversal motion is carried out by detecting the return position and the protrusion completion position of the ejector pin by means of the detection switches. Therefore, the motion is delayed by the time required for the detecting operation, causing an increase in cycle time.
To reliably perform the unmolding operation of the molded product, an air ejector is sometimes used in combination with the ejector pin for the unmolding operation. However, the air ejector is used only to prevent the unmolded piece from being hindered from dropping by riding on the protruding portion of the mold or by sticking to the mold due to static electricity, unmolding agent, etc. Thus, th
REFERENCES:
patent: 5405259 (1995-04-01), Morikita
patent: 5439371 (1995-08-01), Sawaya
patent: 5472335 (1995-12-01), Morikita
Hosoya Yuichi
Kamiguchi Masao
Kobayashi Minoru
Fanuc Ltd.
Mackey James P.
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