摘要：

The specification and drawings disclose poppet-type check valves each comprising a body with a through flow passage and a valve member with a generally circular sealing surface positioned within the passage. The valve member is continually biased toward a seat by a coil spring mounted in the passage. An O-ring positioned in a circumferential groove formed about the passage defines the seat. The groove is open only about the axial side facing the valve member. The inner circumference of the groove is of a lesser diameter than the sealing surface of the valve member. The O-ring is positioned within the groove and has a radial thickness sufficiently greater than the radial width of the groove such that when compressed in the groove, a portion extends out of the open side for engagement with the end face of the valve member. The radially inner wall of the groove is provided with a continuous edge surface which is adapted to engage the end face of the valve member to provide a fixed stop for the valve member. Means for varying the compression on the spring are provided and includes two members threaded axially in the passageway. Each of the members is shown as having a non-circular flow passageway formed through its center. The passageways align in certain positions of relative rotation for adjustment purposes. Thus, adjustment can be accomplished by insertion of an adjusting tool into the flow passage and no external adjustment members are required.

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