US3793803A - Piston actuated automatic drain filter - Google Patents

Abstract

This invention relates to an air line filter of the type having a replaceable filter cartridge adapted to remove both entrained solids and fluids, the latter being dumped automatically by a piston-actuated drain valve each time the air flow shuts off. More specifically, the instant invention relates to an improved version of such filter in which one or more bypass passages break the seal between the valve element and its seat so that the Oring forming the seal is not drawn from its groove into a position where it will be damaged upon a downstream demand that returns the valve to closed position prematurely.

Description

United States tent [1 1 Winter Feb. 26, 1974 PISTON ACTUATED AUTOMATIC DRAIN FILTER Inventor: Jon E. Winter, Lakewood, Colo.

Primary Examiner-Tim R. Miles Assistant Examiner-William Cuchlinski, Jr.

Attorney, Agent, or FirmEdwards, Spangler, ['73] Assignee: Wilkerson Corporation, Englewood, Wymore & Klaas Calif.

[22] Filed: June 21, 1971 [57] ABSTRACT 211 Appl' 155 111 This invention relates to an air line filter of the type having a replaceable filter cartridge adapted to remove both entrained solids and fluids, the latter being [52] US. Cl 55/218, 55/466, 137/204 dumped automatically by a pistomactuated drain [Sl] Int. Cl B0143 33/38 valve each time the flow Shuts ff More Specifi [58] new of Search 55/218 cally, the instant invention relates to an improved ver- 55/466; 137/204 sion of such filter in which one or more bypass passages break the seal between the valve element and its [56] References Cited seat so that the O-ring forming the seal is not drawn IT AT PATENTS from its groove into a position where it will be dam- 2,6l9,l06 11/1952 Wilkerson 137/204 ag d upon a downstream demand that returns the 3,261,146 7/1966 Malec 55/218 valve to closed position prematurely. 3,668,837 6/1972 Gross 55/218 X 2,869,570 1/1959 Wilkerson 137/204 3 Clams, 5 Drawing Figures PATENTEBmaze I974 INVENTOR JON E. WINTER 5 W wfo w TER For some time an air line filter has been successfully marketed in which the air flow is directed through a replaceable tubular cartridge housed inside a hollow body. As the entrained solids impinge against the cartridge wall, they drop out as the result of a conventional screening action. The entrained fluids, on the other hand, pass through the minute capillary passages of the filter element and, because of the resulting drop in pressure, drop out and are collected in a sump.

In the bottom of the bowl is a spool-type drain valve encircled by an O-ring that seals against the cylindrical wall of a tubular seat that has a chamfered generally frustoconical entryway. Fluids collected in the sump in the bottom of the bowl are discharged through the drain valve. This drain valve reciprocates between its seated and unseated positions and actuation thereof is accomplished automatically by means of a springbiased piston that drops down each time the air flow stops. As long as there is a downstream demand, the air pressure against the underside of the piston is sufficient to overcome the spring bias and hold the drain valve closed.

Filters of this type that operate automatically on a demand basis, of course, are subject to repeated actuations with the interval therebetween being relatively short. On occasion, it has been found that the O-ring becomes damaged to the extent that the seal provided thereby fails resulting in a leak. Apparently what actually takes place is that as the spool moves down toward open position, instead of the seal being broken when the O-ring moves onto the chamfered entryway, it expands and maintains brief sealed contact therewith. This occurs because the interior bowl pressure is higher than atmospheric and a differential pressure exists across the O-ring that acts outward radially maintaining the seal even onto the upper part of the flared wall surface rather than breaking it as soon as the O-ring moves down off of the cylindrical surface of the seat. So long as the drain valve spool continues to move down toward open position, no problem arises because eventually the entryway will widen out to a degree where the O-ring can no longer remain in sealed contact therewith. If, on the other hand, a sudden downstream demand occurs which reverses the direction of the valve element before it has opened for enough to break the annular seal, the O-ring will be trapped in this partially extended position where it is subjected to a shearing action as it moves back up across the annular corner defined by the intersecting conical and cylindrical seat surfaces.

It has now been found in accordance with the teaching of the instant invention that this problem can be completely eliminated by the simple, but unobvious, expedient of providing the seat with one or more bypass passages positioned and adapted to instantly drop the bowl pressure to atmospheric as soon as the valve element starts to open thus eliminating the differential pressure condition responsible for expansion of the O- ring into a position where it is subject to the shearing action of the seat corner.

Accordingly, it is the prime object of the present invention to provide a novel and improved cartridge type air filter equipped with bypass means operative to equalize the air pressure inside and outsidethe bowl the instant the valve element starts to open so that the O-ring seal will not expand under the influence of a differential pressure impressed thereacross and move out of its groove into a position where it is subjected to a shearing action at the edge of the seat.

Another object is to provide the aforementioned improved version of the filter without having to alter the basic structure thereof in any manner other than to introduce one or more bypass grooves into the surface of the seat.

Further objects are to provide a filter of the type forming the subject matter hereof that is more reliable than its unimproved prior art counterpart, one that is virtually leakproof except when dumping fluid as intended, and a unit of the class described that is virtually maintenance-free except for periodic replacement of the filter cartridge.

Other objects will be in part apparent and in part pointed out specifically hereinafter in connection with the description of the drawings that follows, and in which:

FIG. 1 is a diametrical section showing the improved cartridge-type filter of the present invention in its entirety;

FIG. 2 is an enlarged fragmentary detail showing the drain valve spool in diametrical section and in closed position;

FIG. 3 is a fragmentary detail much like FIG. 2 and to the same scale revealing the drain valve in open position;

FIG. 4 is a bottom plan view of the drain valve seat showing the bypass passages introduced into the frustoconical entryway thereto;

FIG. 5 is a still further enlarged fragmentary sectional detail showing the O-ring encircling the drain valve spool in relation to the frustoconical entryway to the seat and the groove in the latter that constitutes the bypass by means of which the positive bowl pressure is dumped the instant the O-ring reaches said entryway during its excursion toward open position.

Referring next to the drawings for a detailed description of the present invention and, initially, to FIG. 1 for this purpose, reference numeral 10 has been selected to designate the cartridge-type filter in its entirety while numeral 12 refers to the body thereof and numeral 14 the bowl detachably connected to the latter. The body has an inverted generally cup-shaped configuration, its lower margin being bordered by a planar surface 16 adapted to rest atop a flange l8 encircling the upper end of the bowl and form a fluid tight seal therewith. An integrally formed annular skirt 20 extends down from the top 22 of the body spaced inwardly of the inside surface 24 of its outside wall 26 so as to cooperate therewith in defining an annular cavity 28. The inside surface 30 of this skirt is cylindrical and forms a cylinder wall within which piston 32 reciprocates. An air intake passage 34 connects the exterior of the body with annular cavity 28 through outside wall 26. Air outlet passage 36, on the other hand, connects the interior of the cylinder with the exterior of the body across annular cavity 28 without communicating with the latter.

The interior of the bowl is shaped to define an upwardly facing annular ledge 38 containing an O-ring groove 40 within which is seated an O-ring 42. Resting atop this ledge in continuous annular sealed contact r with the O-ring is a partition wall 44 having an integrally-formed tubular portion 46 that passes down and out through a central opening 48 in the bottom of the bowl where the externally-threaded neck 50 thereof is secured by a nut 52. Nut 52, upon being tightened on the threaded neck, abuts the bottom 54 of the bowl and, in turn, draws the partition wall down into sealed contact atop the O-ring. An external O-ring groove 56 borders the tubular portion 46 above the neck and is provided with an O-ring that seals against the cylindrical wall surface bordering the bowl opening 48.

Bridging the gap between partition wall 44 and the lower margin of skirt is a tubular filter cartridge 58. An upstanding annular flange 60 on the top of the partition wall cooperates with a similar flange 62 on the lower margin of the skirt to hold the cartridge centered therebetween. Air and entrained contaminants entering the air inlet must pass into the annular cavity 28 where the cartridge screens out the solid particles. The air along with the remaining entrained fluids pass through the capillaries of the filter cartridge and are released into expansion chamber 64 at a lower pressure where the fluid contaminants drop out and are collected in the sump at the base thereof.

An upstanding tubular section 66 is formed integrally atop the partition wall and provides a coaxial continuation of the lower tubular section 46. This upper section has a vertical drain slot 68 therein whereby the fluids deposited in the bottom of the sump can drain on down into the lower section 46 where they either pass on out of the bowl past the chamfered entryway 70 to the cylindrical portion 72 of the spool valve seat 74 contained therein or, alternatively, are deposited in a reservoir 76 located between the bottom of the bowl and the portion wall 44. Shunting the fluids off into the reservoir is made possible by ports 78 in the wall of the lower tubular section 46 and this occurs whenever the spool valve 80 is closed.

Piston 32 carries an annular O-ring groove 82 within which is mounted O-ring 84 which reciprocates therewith in fluid-tight sealed contact with the cylinder wall 30. The piston is generally funnel-shaped although the neck 84 thereof has no opening therethrough in the manner of most funnels. Instead, an internally flanged nut 86 screws onto the lower end thereof and is used to loosely fasten and suspend the spool valve therefrom. A coiled compression spring 88 resting atop supports 90 inside the piston bowl 92 and abutting the underside of the top wall of the body normally biases the piston along with the spool valve attached to the bottom thereof into open position. The piston has a bleed port 94 in the wall thereof sized to pass enough air to prevent it from rising against the bias of spring 88 should a leak develop downstream.

During normal operation, the unit dumps moisture each time the air flow stops. Where no air flows, piston 32 is in the lower position thereof shown in FIG. 1 and the fluid in the reservoir 76 will drain from the bowl through ports 78 and lower tubular portion 46. When a downstream demand for air occurs, the air pressure above piston 32 drops to a level where the pressure in chamber 64 exceeds the bias exerted by spring 88 thereby pushing the piston up to a level where the air outlet passage 36 is uncovered and air can flow to satisfy the demand. As this occurs, the spool valve 80 is raised by the piston into closed position against the cylindrical section 72 of the seat 74 thus closing off the reservoir 76. At the same time, however, the upper frustoconical section 96 of the spool valve 70 will leave the cylindrical section 72 of the seat and pass into the oversize interior 98 of the upper tubular section thus allowing fluid to pass under the influence of the positive pressure in chamber 64 through the drain slot 68 and down into the reservoir. Once the air flow. stops, the spring will return the piston and valve to its lower position as the pressure in chamber 68 bleeds off through port 94.

Now, the lower frustoconical section 100 of the spool valve is separated from the enlarged cylindrical section 102 at the end thereof by an annular groove 104 containing an O-ring 106, all of which is revealed most clearly in FIGS. 2, 3 and 5 to which reference will now be made. Looking particularly at FIGS. 3 and 5, it will be seen that as the spool valve raises up and moves into cylindrical seat section 72, the O-ring 106 will first engage the chamfered entryway and be compressed into the bottom of its groove 104. It is then free to ride on up into the cylindrical section of the seat in continuous annular fluid-tight sealed contact therewith as shown in FIG. 2.

The problem arises when the spool valve is moving toward open position and the air pressure in annular cavity 108 between the upper and lower spool sections 96 and exceeds the atmospheric side of the latter. As this condition occurs, the high pressure will enter O-ring groove 104 from above and attempt to maintain the O-ring in sealed contact with the flared surface at the entryway to the seat by stretching and elongating it. If, then, with O-ring 106 no longer bottomed in its groove 104, a downstream air demand causes the spool valve to change direction before such seal has been broken, the O-ring will be caught and pinched between the lower outside corner 110 of said groove and the corner 112 defined by the intersecting conical and cylindrical seat surfaces causing it to be sheared or damaged. The eventual destruction of the O-ring to the point where it will no longer seal the spool-valve within its seat is more or less inevitable.

With reference to all of the figures of the drawing, it can be seen that the above described shortcoming of the prior art drain valve can be eliminated by the simple, but unobvious, expedient of providing the chamfered entryway to the seat with one or more bypass grooves 114 positioned and adapted to instantly equalize the air pressure above and below O-ring 106 just as it leaves the cylindrical section of the seat and before it has an opportunity to expand within its groove 104. In the particular form illustrated, four such grooves 114 are used spaced equidistantly around the entryway. Note in FIG. 5, that just as the O-ring reaches corner 112 on its downward excursion, it will open the bypass passages 114 thereabove and equalize the pressure.

What is claimed is:

1. In an air line filter of the type having a body with an inlet and an outlet connectable into an air line, a bowl detachably connected to the body cooperating therewith to define a pressure chamber, said bowl defining a reservoir adapted to catch fluid contaminants and having a drain opening in the bottom thereof, an upstanding hollow cylindrical drain tube with a chamfered entryway at its lower end mounted within the drain opening, a valve member mounted within the drain tube for reciprocal movement between a closed position in the cylindrical portion thereof and an open position beyond its chamfered entryway, an O-ring seal encircling the valve element in fluid-tight sealed relation to the cylindrical portion of the drain tube, and a the passage forming means comprises at least one groove in the chamfered entryway communicating the interior of the cylindrical portion.

3. The improvement as set forth in claim 2 in which: the groove opens into the cylindrical portion at a point spaced sufficiently far above the entryway to equalize the bowl pressure before the O-ring passes into the chamfered portion.

Claims (3)

1. In an air line filter of the type having a body with an inlet and an outlet connectable into an air line, a bowl detachably connected to the body cooperating therewith to define a pressure chamber, said bowl defining a reservoir adapted to catch fluid contaminants and having a drain opening in the bottom thereof, an upstanding hollow cylindrical drain tube with a chamfered entryway at its lower end mounted within the drain opening, a valve member mounted within the drain tube for reciprocal movement between a closed position in the cylindrical portion thereof and an open position beyond its chamfered entryway, an Oring seal encircling the valve element in fluid-tight sealed relation to the cylindrical portion of the drain tube, and a spring-biased piston-type valve actuating means operatively connected to the valve member and mounted in the bowl for reciprocal movement in response to fluctuations in pressure within the pressure chamber, the improvement which comprises: passage-forming means interconnecting the cylindrical and chamfered portions of one drain tube operative upon movement of the O-ring across the juncture therebetween to equalize the pressure inside and outside of the bowl.

2. The improvement as set forth in claim 1 in which: the passage forming means comprises at least one groove in the chamfered entryway communicating the interior of the cylindrical portion.

3. The improvement as set forth in claim 2 in which: the groove opens into the cylindrical portion at a point spaced sufficiently far above the entryway to equalize the bowl pressure before the O-ring passes into the chamfered portion.

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