Source: {"pile_set_name": "USPTO Backgrounds"}

1. Field of the Invention
This invention relates to a check valve for preventing the reverse flow of gasoline supplied to a tank through an automotive fuel supply pipe.
More specifically, while various check valves have heretofore been proposed and used, the present invention concerns a check valve which can be inserted in a comparatively small diameter pipe such as a fuel supply pipe for supplying fuel to an automotive gasoline tank such that it will not obstruct fuel supply but closes as soon as a reverse flow occurs.
2. Prior Art Statement
As check valves for insertion in liquid supply pipes, there are known those disclosed in Japanese Utility Model Publications SHO 54(1979)-36334, 56(1981)-5638 and 56(1981)-49015.
Of these check valves, those disclosed in the Japanese Utility Model Publications SHO 54(1979)-36334 and 56(1981)-49015 are for insertion in a pipe. Either of these valves is opened by a pressure of liquid flowing in one direction, while it is closed when reverse flow of the liquid occurs. More specifically, each of these valves has two, i.e., upper and lower valve plates. One of these valve plates is pivotally mounted in a pivotal section provided in an inner wall of a valve body, while the other valve plate is pivotally mounted in a pivotal section diametrically crossing a central portion of the valve body. These valve plates are pivotally moved about their pivotal sections when they are opened and closed.
These valves, however, are adapted for use in a large diameter pipe, as disclosed in the aforementioned publications. Therefore, although they do not constitute any substantial obstacle with respect to the flow of liquid when used in a large diameter pipe, they would constitute a great obstacle to flow if used in a small diameter pipe like an automotive fuel supply pipe.
In this case, not only the central pivotal section constitutes an obstacle to flow, but also other pivotal sections projecting from the inner wall of the valve body reduce the effective pipe diameter, thus obstructing the flow, i.e., liquid supply.
In a further aspect, in the prior art check valves, the valve plates are usually closed by their own weight. For this reason, the pivotal section has to be located above the valve plate at all times. If it is located at the wrong position, failure of valve function and other difficulties are likely.