| 摘要 |
A pump has a flapper valve structure with recesses around a valve mounting area that receive locator pins during assembly to locate and retain the flapper valve during assembly, and an armed valve stop. The pump uses tubular transfer members for transferring intake and/or exhaust air into the crankcase and/or between valve head chambers. The pump has compact 180° opposed pistons that minimize axial spacing between the pistons on the drive shaft and thereby reduces the shaking couple and noise from reciprocation. Each piston has its own eccentric element press-fit into the connecting rods so as not to occupy space between the pistons. The shaking couple can be further reduced for pistons of different masses by selecting the mass of the cup retainers to compensate for the difference in overall piston masses. The pump includes an improved cylinder sealing, arrangement having a circumferential groove in an angled surface at the end of the cylinder. The pump also has a special cover and seal for closing the open neck of the pump crankcase and a multi-lobed valve stop.
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