The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 05, 2000
Filed:
Jul. 30, 1998
Hitoshi Hara, Funabashi, JP;
Abstract
A back-flow prevention apparatus is composed of a screw and a platelike closing member. The screw includes at least a metering portion having a groove formed thereon for advancing a resin. The closing member is brought into an open position state by resin pressure which is developed behind the closing member in association with metering, thereby establishing communication between the groove and a space located ahead of the screw. The closing member is brought into a closed position by a restoring force of an elastic material, thereby shutting off communication between the groove and the space located ahead of the screw. Upon completion of a metering step, the restoring force brings the closed position into the closing state to thereby shut off communication between the groove and the space located ahead of the screw. Accordingly, sealing can be completed before the start of an injection step. Further, since timing for shutting off communication between the groove and the space located ahead of the screw does not vary, not only can the amount of resin charged into a mold cavity be stabilized, but also variation in injection peak pressure can be suppressed. As a result, molded products can be prevented from suffering burrs, short shot, or like defects. Also, variation in weight among molded products can be suppressed.