Conveyors: power-driven – Conveyor section – Endless conveyor
Reexamination Certificate
1999-08-30
2001-06-26
Hess, Douglas (Department: 2167)
Conveyors: power-driven
Conveyor section
Endless conveyor
C198S853000, C198S957000
Reexamination Certificate
active
06250458
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a conveyor chain having a multiplicity of links pinned together and each including a flat load-carrying portion for carrying thereon an article to be conveyed by the conveyor chain. More particularly, this invention relates to a low friction coefficient plastic conveyor chain particularly suitable for use in an accumulate conveyor by which articles are accumulated at a given position on the conveyor chain while they are slipping on the flat load-carrying portions during continuous traveling of the conveyor chain, or a sorting conveyor by which articles are sent out from or collected into a given position on the flat load-carrying portions while the conveyor chain travels continuously.
2. Description of the Related Art
In a conveyor chain designed for use in the applications described above, links as a whole or at least flat load-carrying portions of the links are required to have a small friction coefficient so that articles can slip on the flat load-carrying portions. To meet with this requirement, the links or the flat load-carrying portions are conventionally formed from a synthetic resin material composed of a polyacetal resin blended with a fluorine resin or a long-chain alkyl ester-based lubricant.
The conventional plastic conveyor chain has been found unsatisfactory as a container having a relatively unstable bottom configuration, such as a petaloidal-shaped PET (polyethylene terephthalate) bottle, has recently distributed in the market. This is because containers having such unstable bottom configuration are liable to fall over during conveyance or as they are caused to slip on the flat load-carrying portions of the conventional plastic conveyor chain.
To deal with this problem, two approaches have been taken. According to a first prior approach, chamfered front and rear corner edges of each flat load-carrying portion and the spacing between adjacent links are made small so as not to catch the bottoms of the containers. A second approach relies on a satin finishing effected on the load-carrying surface to reduce a contact area relative to the containers, thereby decreasing a frictional resistance between the satin-finished load-carrying surface and the containers.
The first approach is found somewhat successful, but the second approach is not because the satin-finished load-carrying surface becomes worn away in a relatively short time. Since the worn-out load-carrying surface has an increased friction coefficient, causing the container falling-over problem to recur.
From the still unsatisfactory results of the prior approaches, the present inventors have concluded that the links as a whole or at least the flat load-carrying portions of the links need to be formed from a material having a smaller friction coefficient than the materials used in the conventional conveyor chain.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a conveyor chain composed of a multiplicity of pinned links each having a low friction coefficient flat load-carrying portion formed from a specific synthetic resin material or compound.
To achieve the foregoing object, the present invention provides a conveyor chain comprising a multiplicity of links pivotally connected together by pins, each of the links having a flat load-carrying portion for carrying thereon an article to be conveyed by the conveyor chain. At least the flat load-carrying portion of each link is formed from a synthetic resin material of a composition comprising a polyacetal resin and a silicone-containing lubricant.
The flat load-carrying portion of the conveyor chain has a smaller kinematic friction coefficient than the corresponding portion of the conventional conveyor chain and hence is able to achieve stable conveyance of articles for a long time even when the articles have an unstable bottom configuration. During accumulation or sorting of the article, a frictional resistance acting between the flat load-carrying portions and the articles can be maintained at a considerably small value. Thus, the conveyor chain can travel under reduced tension, has a long service life, and can operate at a reduced running cost.
Preferably, the silicone-containing lubricant contains, with respect to the weight of the synthetic resin material, 0.5 to 2.0% by weight of silicone oil, 0.5 to 2.0% by weight of potassium titanate fiber, and 0.5 to 2.0% by weight of fatty ester obtained from a monobasic fatty acid and a monohydric alcohol.
The above and other objects, features and advantages of the present invention will become apparent to those versed in the art upon making reference to the following detailed description and the accompanying sheets of drawings in which a certain preferred embodiment incorporating the principle of the present invention is shown by way of illustrative example.
REFERENCES:
patent: 5309705 (1994-05-01), Takahashi et al.
patent: 5559180 (1996-09-01), Takahashi et al.
patent: 6068112 (2000-05-01), Kasai et al.
Ishii Takashi
Kubayashi Toshio
Murakami Yoshihiro
Sanada Daisuke
Shibayama Katsutoshi
Dann Dorfman Herrell and Skillman, P.C.
Hess Douglas
Skillman Henry H.
Tsubakimoto Chain Co.
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