Engine driven dry air pump with a flange mounted oil drain
Mounting end of an engine-driven accessory includes a longitudinally-extending neck having imperforate lateral surfaces defining a central bore. A flange having a mounting face is disposed at the end of neck.
A plurality of generally radially extending drain passages are formed through the flange, which communicate with the central bore to form a fluid flow path between the bore and the exterior of the flange. A seal is provided for blocking selected ones of the drain passages while leaving the remainder of the drain passages open. The accessory may include a cover having an integral sealing rim which cooperates with a notch in a mating component to compress a portion of a resilient seal while simultaneously allowing for expansion of the remainder of the seal.
A dry air type rotary vane pump usually has a rotor with radial slots, vanes that reciprocate within these slots, and a chamber contour within which the vane tips trace their path as they rotate and reciprocate within their rotor slots. Thereciprocating vanes thus extend and retract synchronously with the relative rotation of the rotor and the shape of the chamber surface in such a way as to create cascading cells of compression and/or expansion, thereby providing the essential componentsof a pumping machine.
Because dry air pumps do not use a liquid lubricant, forms of dry lubrication have been developed. For example, vanes for rotary pumps have been manufactured from carbon or carbon graphite. These parts rub against other stationary or movingparts of the pump during operation. Graphite dust from these parts is deposited on the opposing parts by the rubbing action and forms a low friction film between the parts, thereby providing lubrication. The deposited graphite film is itself worn awayby continued operation of the pump, and is eventually exhausted out of the pump. The film is replaced by further wear of the carbon graphite parts. Thus, lubrication is provided on a continuous basis that continuously wears away the carbon graphiteparts.
One of the primary causes of carbon vane dry pump failure is contamination with engine lubricating oil. If engine lubricating oil passes through the drive system into the interior of the pump in moderate quantities, it will mix with the graphitedust to form a viscous sludge which has poor lubricating properties. This causes overheating and eventual seizing and failure. Because the seals used at the air-oil interface of commercially available pumps and drives are not 100% effective, drainopenings are usually provided for draining any leaking oil before it reaches the carbon vanes. However, the drain openings used in the prior art require that a significant portion of the pump housing fill with oil before it drains.
This causes theshaft to pick up and sling the oil through drain openings in several directions from the pump. This makes it difficult to determine the source of an oil leak. Furthermore, this drain arrangement collects a significant quantity of oil at the air-oilinterface which increases the probability that the oil will migrate into the vane chamber. Finally, because the drains are usually arrayed all the way around the pump to create a “universal” fit air pump, the drive area is open and can be easilycontaminated, for example during an engine solvent wash.
The above-mentioned need is met by the present invention, which provides a dry air pump for being attached to an oil-lubricated engine, having: a housing containing a plurality of movable engine-driven vanes for pumping a fluid; and alongitudinally-extending neck with imperforate lateral surfaces defining a central bore. A first end of the neck is attached to a working portion of the accessory, and a flange disposed at an opposite end of the neck from the first end, said flangehaving a mounting face.
A plurality of generally radially extending drain passages are formed through the flange. The drain passages communicate with the central bore to form a fluid flow path between the bore and the exterior of the flange.
According to another embodiment of the present invention, the cover is a drive cover including a longitudinally-extending neck having imperforate lateral surfaces defining a central bore. A flange is disposed at an end of the neck. The flangehas a mounting face, wherein a plurality of generally radially extending drain passages are formed through the flange. The drain passages communicate with the central bore to form a fluid flow path between the bore and the exterior of the drive cover.
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