Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
1998-12-31
2001-02-06
Heitbrink, Jill L. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
C425S149000, C425S587000
Reexamination Certificate
active
06183682
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and to an apparatus for preventing the occurrence of impact pressure in an injection molding machine, in order to prevent impact which would otherwise be induced in an injection step by a hydraulic pressure which builds upon the start of injection.
2. Description of the Relevant Art
Conventionally, there are known two screw driving systems for injection molding machines; i.e., a hydraulic drive system and a motor drive system.
As disclosed in Japanese Patent Application Laid-Open (kokai) No. 8 (1996)-25450, in a conventional injection molding machine which employs a hydraulic drive system, a servo valve is changed over upon the start of injection in an injection step so as to supply pressure oil from a hydraulic oil source to the rear oil chamber of an injection cylinder. The supplied pressure oil causes a screw to advance from an injection start position, thereby injecting a measured amount of resin into and filling a mold. Oil contained in the front oil chamber of the injection cylinder returns to an oil tank through an oil transfer line.
Upon the start of the injection, high-pressure oil is supplied into the rear oil chamber of the injection cylinder in an impactive manner, and thus associated impact acts on oil contained in the oil transfer line via a piston, causing a so-called water hammer phenomenon. This water hammer phenomenon is substantially of a negligible degree for ordinary injection molding machines. However, for injection molding machines having a high injection speed, the degree of water hammer cannot be disregarded. Specifically, water hammer becomes obvious in the form of a considerably loud noise (impact sound) or significant vibration, and associated impact pressure has an adverse effect on a hydraulic circuit and hydraulic devices.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and an apparatus for preventing the occurrence of impact pressure in an injection molding machine and capable of reliably preventing the occurrence of the water hammer phenomenon to thereby eliminate associated detrimental noise and vibration.
Another object of the present invention is to provide a method and an apparatus for preventing the occurrence of impact pressure in an injection molding machine which can be embodied easily and at low cost and exhibit a wide range of usability such as the application to an existing injection molding machine.
To achieve the above objects, the present invention provides a method for preventing the occurrence of impact pressure in an injection molding machine, wherein gas (air) is supplied into an oil transfer line extending between a front oil chamber of an injection cylinder and an oil tank during a molding cycle, excluding an injection step, thereby preventing impact which would otherwise occur due to oil pressure generated upon the start of injection in the injection step.
The present invention further provides an apparatus for preventing the occurrence of impact pressure in an injection molding machine, comprising a gas supply section for supplying gas (air) into an oil transfer line extending between a front oil chamber of an injection cylinder and an oil tank during a molding cycle, excluding an injection step.
According to the present invention, gas is supplied into the oil transfer line extending between the oil tank and the front oil chamber of the injection cylinder during a molding cycle, excluding an injection step. Thus, immediately before the start of the injection step, the oil transfer line becomes empty of or almost empty of oil. Accordingly, even when high-pressure oil is supplied into the injection cylinder in an impactive manner upon start of injection, pressure oil ejected from the injection cylinder flows swiftly through the oil transfer line, thereby preventing occurrence of a water hammer phenomenon.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and of the scope of the invention will become apparent to those skilled in the art form this detailed description.
REFERENCES:
patent: 3604205 (1971-09-01), Geselbracht et al.
patent: 5443782 (1995-08-01), Nakamura et al.
patent: 5641523 (1997-06-01), Shioiri et al.
patent: 5688535 (1997-11-01), Koda et al.
patent: 5906778 (1999-05-01), Arai et al.
patent: 8-25450 (1996-01-01), None
Miyajima Masahiko
Shimizu Ken'ichi
Tanemura Daiki
Birch & Stewart Kolasch & Birch, LLP
Heitbrink Jill L.
Nissei Plastic Industrial Co. Ltd.
LandOfFree
Method for preventing occurrence of impact pressure in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for preventing occurrence of impact pressure in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for preventing occurrence of impact pressure in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2558653