| 摘要 |
A fluid limit valve, comprising: a valve body having aligned valve bore and stem counterbore; transverse input and output fluid channels opening into the valve bore; a valve member slidable in the valve bore; and a spring-pressed, telescopic valve extension or stem slidable in the stem counterbore, is provided with means for producing a fluid signal in response to overtravel of the stem and valve member, comprising: a poppet valve counterbore aligned with the valve bore and containing a poppet valve including a cup-shaped poppet cylinder partially closed by a centrally-apertured poppet seat; a headed poppet loosely slidable in the cylinder and seat with a shank thereof extending toward but normally spaced from the valve member, a ring seal between the poppet and the seat, and a coil spring in the cylinder biasing the poppet toward the valve member and compressing the ring seal; fluid channels in the valve body and poppet cylinder wall connecting the interior of the cylinder with an input channel, for pressurizing the cylinder; and a fluid signal channel connected to the closed space between the valve member and the poppet valve; whereby excessive movement of the stem and valve member in overtravel beyond the normal operating stroke of the valve causes the valve member to engage and move the poppet, thereby opening the fluid seal and admitting fluid from the poppet cylinder to the space and fluid signal channel. The stem spring is weaker than the poppet spring, to permit a predetermined amount of overtravel before the poppet valve is opened and the fluid signal is produced. The invention is disclosed as applied to both double and single land valves.
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