| 摘要 |
<p>The pump has a piston (11) fitting tightly in a cylinder (10) and reciprocating in it. The outer surface of the piston has three circumferential grooves (12, 13, 14) in it. Each groove has one radial hole (16, 17, 18) leading from it in to a central axial bore (20) in the piston. This bore is open on the working face of the piston. As the piston reciprocates the medium pumped enters the grooves from the central bore and lubricates the piston. The leakage from this lubricating action returns to the throughput and therefore does not affect the accuracy of the metering.</p> |
