Hollow, resin mechanical part having a shaft integrally formed t

Details Hollow, resin mechanical part having a shaft integrally formed t Hollow, resin mechanical part having a shaft integrally formed t

1996-06-13

1998-06-30

Theisen, Mary Lynn

Stock material or miscellaneous articles

Hollow or container type article

Polymer or resin containing

264572, 2643288, 26432812, B29C 4500, B29C 4906

Patent

active

057731098

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a hollow, resin mechanical part having a shaft integrally formed therewith. More particularly, the present invention is concerned with a hollow, resin mechanical part having a shaft integrally formed therewith, comprising a hollow, integral, functional segment-shaft structure comprising at least one functional resin segment, and a resin shaft coaxially, integrally formed with the functional segment, wherein the hollow of the hollow, integral segment-shaft structure has a relatively large specific length ratio relative to the entire length of the integral segment-shaft structure. The mechanical part of the present invention has not only high dimensional precision and excellent material-recycling characteristics, but also can be produced with high productivity. The present invention is also a concerned with an injection molding method for producing this mechanical part.
2. Discussion of Related Art
Mechanical parts having a shaft unitarily formed therewith are widely used in various fields, such as automobiles, ordinary machinery, precision machinery and electric and electronic equipment.
In general, a resin mechanical part having a shaft unitarily formed therewith is produced by (1) an insert molding method in which a metallic shaft is used, (2) a method in which a mechanical part is carved out of a resin mass, or (3) a hollow injection molding method.
At the outset, method (1) mentioned above is explained. A molten resin undergoes shrinkage upon cooling. Therefore, when a non-hollow, resin mechanical part having a shaft integrally formed therewith is produced by injection molding, the resin thickness inevitably becomes large and, therefore, the shrinkage of the resin should also become large, so that the resin mechanical part becomes poor in dimensional precision. The dimensional precision of a mechanical part is usually expressed in terms of the coaxality and the degree of "run out". When the mechanical part is a toothed wheel (gear), the dimensional precision also includes the dimensional precision of teeth, and when the mechanical part is a roller, the dimensional precision also includes cylindricality. When a non-hollow, resin mechanical part having a shaft integrally formed therewith is produced by injection molding, there is also a disadvantage in that the time required for solidifying the molten resin is prolonged due to the large resin thickness, so that the cycle time of molding is prolonged, leading to a low productivity. For solving the above problems, method (1) mentioned above, i.e., an insert molding method using a metallic shaft was proposed in which an increase in the resin thickness can be avoided.
Method (2) mentioned above, in which a mechanical part having a shaft integrally formed therewith is carved out of a resin rod or the like, is advantageous in that there is no problem of shrinkage of the resin and a mechanical part having a good dimensional precision can be obtained.
Examples of method (3) mentioned above, in which a mechanical part having a shaft integrally formed therewith is produced by hollow injection molding, are disclosed in Unexamined Japanese Patent Application Laid-Open Specification No. 5-208460 and DE Publication No. 3835964. In each of these publications, a molten resin is injected into a mold cavity to form a molten resin mass in a manner such that a space substantially non-filled with the molten resin mass remains in the cavity, and, subsequently, a gas is introduced into the molten resin mass to form a hollow within the molten resin mass, thereby forming a shaped, hollow resin article. This method was proposed so as to simplify the process for producing a roller having a shaft integrally formed therewith and to achieve lightness in the weight of a mechanical part (and also to improve economy due to a decrease in the amount of a resin to be used).
However, method (1) mentioned above is disadvantageous in that it is necessary to involve an additional step in which a metallic sha

REFERENCES:
patent: 5028377 (1991-07-01), Hendry
patent: 5173241 (1992-12-01), Shibuya et al.
patent: 5612067 (1997-03-01), Kurihara et al.

Affiliated with

Also associated with

Rating

Hollow, resin mechanical part having a shaft integrally formed t does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Hollow, resin mechanical part having a shaft integrally formed t, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hollow, resin mechanical part having a shaft integrally formed t will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1856721