Importance

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Abstract

A safety valve apparatus (25) for feeding predetermined liquid (21) from a tank (22) to a diaphragm pump (1) in which a central rod (3) is reciprocally slidable by air pressure to forcibly pump out the liquid. The safety valve apparatus includes a housing (27, 28, 29) having a space (40) including a liquid balance port (28a) that is always in communication with the liquid in the tank, and a liquid chamber (31) including a liquid flow-in port (29a) into which the liquid from the tank flows, and a liquid flow-out port (29b) from which the liquid from the tank flows out. A valve rod slidably passes through the housing and is provided at its end near the liquid chamber (31) with a valve body (45) that is capable of being seated in the flow-in port (29a). Also, a diaphragm (34) is disposed within space (40) so as to be attached between the valve rod (32), which protrudes into the space (40), and an inner peripheral wall of the space. The diaphragm partitions the space (40) into at least a liquid balance chamber (41), communicating with the liquid balance port (28a), and another chamber (42). In this case, an effective liquid pressure receiving area of the diaphragm (34) is larger than an effective liquid pressure receiving area of the valve body (45), such that, when the diaphragm pump is in an inoperative condition, the valve rod (32) slides toward the liquid chamber (31) to close the liquid flow-in port (29a), and, when the diaphragm pump is operated to generate negative pressure in the liquid chamber (31), the valve rod (32) slides toward the liquid balance chamber (41) to open the liquid flow-in port (29a). Accordingly, if the diaphragm pump is damaged, the safety valve prevents liquid from flowing toward the diaphragm pump and contaminating the surrounding environment.

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First Claim