Gas separation – Plural serial basically diverse separating media – Plural stages in unitary casing
Patent
1994-02-15
1995-04-25
Bushey, Charles S.
Gas separation
Plural serial basically diverse separating media
Plural stages in unitary casing
55322, 55323, 55325, 55462, 55523, 55DIG17, 95268, B01D 4600
Patent
active
054095140
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an air filter. It relates particularly to an air filter for removing particulate matter, water and oil, whether in the form of vapour or droplets, from compressed air systems such as air braking systems.
2. Description of the Prior Art
Hot compressed air has a greater propensity for carrying water and oil vapour and suspended water and oil droplets and other particles than has non-compressed room temperature air. It is therefore frequently important for filtering apparatus to be provided for removing contaminants from a system which utilizes compressed air.
Conventional systems for removing contaminants have involved cooling by means of an air cooler which encourages precipitation of water and oil vapours, followed by passage through a porous filter medium which removes suspended water and oil droplets and other foreign particles. However, the air coolers used in such systems have generally been large and expensive, and the porous filter medium has generally become blocked in a short period of time so that frequent maintenance or replacement has been required.
Over the past few years, more efficient means of removing vapours from compressed air have been developed. Examples of these new types of humidity removers are given in U.S. Pat. No. 4,662,907, International Publication No. WO88/02658 and U.S. Pat. No. 4,848,988. Each of these specifications describes a device having an inner cylinder completely encompassed within an outer cylinder. Compressed air is injected through flared nozzles located near the top of the inner cylinder, and the inner cylinder functions as an expansion chamber in which the air expands rapidly and so cools adiabatically. Cooling results in precipitation of vapours, and the devices described in U.S. Pat. No. 4,662,907 and International Publication No. WO88/02658 provide filter nets across the inner chamber to trap droplets so precipitated. The device disclosed in U.S. Pat. No. 4,848,988 relies on a baffle plate to trap precipitated droplets. The water and oil then flows down the sides of the inner chamber and accumulates at the bottom of the outer chamber, from which it may be removed by an outlet port. The dried air passes from the bottom of the inner chamber into the outer chamber and out through an outlet port at the top of the outer cylinder.
While these types of filters are effective in removing oil and water from compressed air, it has been found that after a short period of use the flared injection nozzles located at the top of the inner cylinder frequently become blocked by particles, oil and moisture, so that regular servicing is required.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an air filter overcoming some of these disadvantages.
According to the present invention, there is provided an air filter comprising: passes, to strain particulate matter from the air; passes; that droplets of air and water precipitate and accumulate at the bottom of the expansion chamber; and
It is preferred that a baffle be provided between the inlet and the porous filter means in the prefiltration chamber in order to disperse the air around the prefiltration chamber so that the full impact of incoming air is not directed only against one part of the porous filter means.
It is further preferred that the porous filter means be substantially cylindrical, conical or frusto-conical in shape with a flat base, such that air passes through the filter means into a substantially hollow core and out through the base towards the venturis.
It is preferred that a condensation accumulator plate be provided in the expansion chamber directly adjacent the venturis such that air, oil and moisture from the venturis passes directly onto the condensation accumulator plate.
It is further preferred that the expansion chamber comprise an internal chamber and an external chamber such that air from the venturis passes first through the internal chamber and then through the external chamber.
BRIEF DESC
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Bajada Jimmy P.
Ragusa Guiseppe
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