Overfill preventing valve

Abstract

An overfill preventing valve (20) is adapted to be operatively interposed in a flow path between a fluid source (21) and a compressed fluid storage cylinder (22) to prevent the cylinder from being overly filled. The improved valve includes an elongated tubular body having a first seat (25), a first space (26), a second space (28), a second seat (29), a third space (30), a third seat (31), a fourth space 37 and an entrance portion (32) communicating with a source. A passageway (33) continuously communicates the first and fourth spaces. The second and fourth spaces communicate with the interior of the cylinder. A float (36) is contained within the body for movement toward and away from the first seat in response to the liquid level in the cylinder. A valve member (38) is mounted on the body for sealed movement toward and away from the second seat. This valve member separates the first space from the second space. The valve member is biased to move away from the second seat. A piston (40), separating the third space from the fourth space, is mounted for sealed sliding movement therealong toward and away from the third seat. The piston is biased to move toward the third seat. The piston has a variable-area orifice communicating the entrance portion with the third space. The cross-sectional area of this orifice varies as a function of the direction of the flow. When it is desired to fill the cylinder and the float does not engage the first seat, incoming fluid displaces the piston away from the third seat and flows from the entrance portion into the cylinder via the fourth space. However, when the float sealingly engages the first seat, the valve member is caused to sealingly engage the second seat, and the piston is caused to sealingly engage the third seat to prevent further incoming flow from the source to the cylinder.