Diaphragm type air pump

Abstract

A diaphragm is interposed between first and second housings to form first and second diaphragm chambers at both sides thereof for pumping out air in accordance with expansion and contraction of the chambers. A shaft for reciprocally moving the diaphragm is connected thereto at one end and extends through a hole formed in a bushing which is fixed to the second housing. A lever is pivotally secured to the housing to perform a pivotal movement and operatively connected at its inner end to the other end of the shaft in a lever compartment of the housing and at its outer end to an eccentric cam formed on an engine crankshaft, so that the motion of the cam is transmitted to the shaft as the reciprocal movement through the pivotal movement of the lever. A bellows is disposed in the second diaphragm chamber surrounding a portion of the shaft, wherein the upper and lower ends are respectively and air-tightly connected to the diaphragm and the bushing to form a bellows chamber. An axially extending groove is formed on either the inner surface of the hole or the outer surface of the shaft, so that the bellows chamber is communicated with the lever compartment by the groove. The compartment is communicated with an engine crankcase and thereby filled with a large amount of engine oil mist. The bellows chamber is also subjected to expansion and contraction in accordance with the reciprocal movement of the shaft to alternately draw into and force out air in the compartment, so that a portion of the mist is forcibly introduced into the groove to lubricate the shaft and the bushing.