| 摘要 |
A positive displacement pump for forcing semi-fluid materials and especially concrete into a delivery pipe for transmission to a remote location, comprising a pair of parallel pump cylinders having mouths opening to a feed chamber in which a swivel valve having an S-shaped lengthwise extending material conducting passage is mounted for oscillation about a fixed axis that is equispaced from and parallel with the axes of the pump cylinders, alternately between two defined positions in each of which the mouth of one of the pump cylinders is uncovered to enable material in the feed chamber to be inducted into that cylinder by retraction of its piston and the other cylinder is communicated with the delivery pipe by means of the material conducting passage of the valve, the pump being characterized by the fact that the loads imposed on the swivel valve by the force of the discharging pump cylinder are transmitted to and carried by the bottom wall of the feed chamber by virtue of the fact that the bottom outer surface of the valve, for the major portion of its axial dimension, is a segment of a frustum of a cone and the inner surface of the feed chamber bottom is shaped to have an area thereof closely contiguous to that conical bottom surface of the valve in all positions of the valve.
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