Patent Publication Number: US-4548624-A

Title: Hygroscopic breather cap

Description:
This is a continuation of application Ser. No. 514,459, filed July 15, 1983, now U.S. Pat. No. 4,504,289. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a breather cap for a liquid petroleum tank and is intended to insure that the air passing into the petroleum tank is both clean and dry. 
     The problems associated with the contamination of petroleum fluids are well known. As the enclosed oil in an industrial machine cools when the operation of the machine ceases, a partial vacuum is typically created in the oil reservoir. This partial vacuum draws air into the oil reservoir. Unfortunately, the air drawn into the reservoir is often contaminated with dust and with moisture. As a result, the oil within the tank is contaminated and must be periodically changed to avoid damage to the machine it lubricates. 
     Not only is the oil directly contaminated by the dust and moisture in the air, the presence of moisture within the oil reservoir often causes oxidation of the oil reservoir itself and the oxidation products serve as a further contaminant to the oil. 
     The filtering of the air entering an oil reservoir to remove dust particles is well known and is shown for example in the Risse et al U.S. Pat. No. 3,160,487 dated Dec. 8, 1964, the Fisher U.S. Pat. No. 3,244,314 dated Apr. 5, 1966 and the Claar U.S. Pat. No. 3,546,853 dated Dec. 15, 1979. In filters of this type, air is generally permitted to pass upwardly through apertures in the bottom of the filter, through a filter material, and then downwardly into the oil reservoir. However, such systems do not provide for the removal of moisture from the air. 
     Attempts have been made to dry the air entering an oil reservoir. In systems such as illustrated in the McCall U.S. Pat. No. 2,603,308 dated July 15, 1952, air is permitted to pass upwardly through a filter element into a cavity containing a desiccant. Such systems generally do not provide for the viewing of the desiccant without removal of the filter cap and the periodic removal of the filter cap to check the condition of the desiccant results in increased contamination. Failure to check the desiccant at periodic intervals increases the likelihood that the desiccant will be contaminated and thus not effective. 
     A further problem with systems such as illustrated in the McCall patent is that the air passing into the dust filter may pass through the dust filter into the oil reservoir without passing through the desiccant. In this way, the value of the desiccant to the system may be materially reduced. 
     It is accordingly an object of the present invention to obviate these and other deficiencies of such known systems and to provide a novel hygroscopic breather cap for a petroleum tank such as an oil reservoir. 
     Another object of the present invention is to provide a novel hygroscopic breather cap in which dust is removed from the air prior to passage through the desiccant. 
     Yet another object of the present invention is to provide a novel hygroscopic breather cap for a liquid petroleum tank which the air entering the tank is forced to pass through a substantial volume of desiccant. 
     A further object of the present invention is to provide a novel hygroscopic breather cap which prevents the passage of desiccant fines into the petroleum tank. 
     Still a further object of the present invention is to provide a novel construction for a hygroscopic breather cap in which the condition of the desiccant may be readily observed without exposing the contents of the petroleum tank or the desiccant to the atmosphere. 
     Still a further object of the present invention is to provide a novel construction for a hygroscopic breather cap in which the effective air input openings may be easily increased in the field to adapt the breather cap for a particular application. 
     These and many other objects and advantages of the present invention will be readily apparent from the claims and from the following detailed description when read in conjunction with the appended drawings. 
    
    
     THE DRAWINGS 
     FIG. 1 is a pictorial view in elevation of one embodiment of the hygroscopic breather cap of the present invention in partial section illustrating the construction thereof; 
     FIG. 2 is an alternative embodiment of the top portion of the breather cap of FIG. 1; 
     FIG. 3 is an exploded view of the breather cap illustrated in FIG. 2 illustrating the treatment of the air passing therethrough; 
     FIG. 4 is a pictorial view in elevation of a third embodiment of the hygroscopic filter cap of the present invention in partial section; and 
     FIG. 5 is a section taken through lines 5--5 of FIG. 4. 
    
    
     THE DETAILED DESCRIPTION 
     With reference to FIG. 1, the breather cap of the present invention may be provided with a cylindrical body 10, a bottom end cap or closure plate 12 and a removable top 14. Disposed within the body 10 is a standpipe 16 which may be connected by a suitable conventional means to a petroleum tank 18 such as an oil reservoir of an industrial machine. 
     For example, the tank 18 may be provided with a conventional male fitting and the standpipe 16 of the present invention connected thereto by means of a relatively stiff rubber or plastic sleeve 20 with sufficient resiliency to receive the standpipe 16 and the fitting of the tank 18 in an air impervious and physically supported relationship. Alternatively, the breather cap of the present invention may be internally or externally threaded to mate with a conventional threaded fitting on the tank 18. 
     As illustrated in FIG. 1, the standpipe 16 passes through a central aperture in the bottom of the body to a position adjacent the closed upper end thereof. The lower end cap may be provided with a plurality of apertures 22 open to the atmosphere and the annulus between the standpipe 16 and the body 10 defines a radially outer passageway for air passing from the bottom of the breather cap to the closed upper end thereof. 
     With continued reference to FIG. 1, air entering the apertures 22 pass through a washer-shaped filter element 24 where dust particles may be removed. This filter element 24 may be of any suitable conventional type but is desirably comprised of a knitted polyester fabric with good releasing characteristics when agitated or subjected to a revenue air flow. Felt may also be used, but generally is less desirable because of the tendency of particles to embed. 
     The radially outer passageway may be filled along its length with any suitable conventional desiccant such as a silica gel, typically one in which the color changes, e.g. from blue to pink, as a function of the saturation of the desiccant with moisture. Desiccants may be mixed to combine the indicating characteristics with other characteristics. 
     With continued reference to FIG. 1, the upper end of the standpipe 16 may be provided with a foam element 26 which serves to increase the effective surface area of the open upper end of the standpipe 16. This material may be of any suitable conventional material such as a 30 to 45 PPI foam with or without charcoal and serves the additional purpose of preventing the passage of desiccant fines into the standpipe 16 and thus into the tank. 
     In operation, air passes upwardly through the radially outer apertures 22, through the dust filter 24, throgh the desiccant 25 along the vertical length of the breather cap, and through the foam material 26 into the top of the standpipe 16. In this way, the air is passed successively through a dust filter, a desiccant, and a desiccant fine filter before passage into the petroleum tank is permitted. 
     As illustrated in FIG. 1, a transparent window may be provided in the top 14 of the filter so that the condition of the desiccant adjacent the open end of the standpipe 16 may be observed without removal of the filter from its operational status. In this way, the condition of the filter furthest from the air inlet, and thus the last of the desiccant to be contaminated, may be readily observed and the breather cap removed only when necessary for recharging with desiccant. 
     In the embodiment illustrated in FIG. 2, a second washer-shaped filter 28 may be provided atop the desiccant 25. It may be held securely in place by a foam member 30 which fills the cavity within the top 14. The functional operation of the filter constructed as illustrated in FIG. 2 may be seen in FIG. 3 where air passes through the first filter 24, through the desiccant 25, through the second filter 28 into the air pervious foam member 30 located in the top 14 of the breather cap. From there, the air passes downwardly into the open top of the standpipe 16 (not shown in FIG. 3) and into the petroleum tank. 
     An alternative embodiment is illustrated in FIGS. 4 and 5. With reference to FIG. 4, a standpipe 32 may be used to carry a generally cylindrical body 34 by virtue of an end or closure plate 36. As illustrated in FIGS. 4 and 5, the closure plate 36 may have a cylindrical sleeve portion 38 adapted to engage the standpipe 32 in an air impervious relationship. 
     As shown in FIG. 5, the central sleeve 38 may be connected to the side walls by means of a plurality of spaced ribs 42. These ribs 42, as well as the sleeve 38, may be used to support a first fabric filter 44. Additional support for the filter 44 may be provided by a first air impervious foam member 46. 
     As shown in FIG. 5, the central sleeve 38 may be connected to the side walls by means of a plurality of spaced ribs 42. These ribs 42, as well as the sleeve 38, may be used to support a first fabric filter 44. Additional support for the filter 44 may be provided by a first air impervious foam member 46. 
     The closure plate 36 may also be provided with a number of structurally weakened areas 40 around the periphery of the central sleeve 38 so that these areas may be readily removed in the field to selectively vary the effective air intake area of the breather cap. These areas may be of the &#34;knock-out&#34; type or alternative simply thin-walled so that one or more thin-walled areas may be easily removed in the field by a screwdriver or other readily available tool. 
     With continued reference to FIG. 4, a second washer-shaped fabric filter 48 may be placed atop the desiccant 47 and held in place by a second air pervious foam member 50 which fills the removable cap 52 of the breather cap. 
     As illustrated in FIG. 4, air entering the apertures 40 in the closure plate 36 at the bottom of the breather cap, successively passes through the first foam member 46, a first fabric filter 44, the desiccant 47, through the second fabric filter 48, and the second foam member 50 into the open top of the standpipe 32. 
     The entire body 34 of the breather cap may be made of a transparent material such as a clear plastic so that the condition of the desiccant 46 may be readily observed therethrough over the entire length of the filter cap. 
     ADVANTAGES AND SCOPE OF INVENTION 
     The present invention significantly reduces the problems of water contaminated oil, and rust inside the petroleum tank. In addition, it provides improved particulate filtration, improved oil oxidation stability and increases oil integrity. Abrasive wear of the industrial machines is reduced as is the attendant downtime and maintenance costs. Moreover, the condition of the unit is constantly available without taking the unit out of service. 
     The breather cap of the present invention provides for filtering of dust particles before the air reaches the desiccant and ensures a prolonged passage of the air through the desiccant. A second filter is provided to prevent the passage of desiccant fines into the petroleum tank. 
     The construction of the breather cap is simple, thus facilitating installation and varying of the effective air intake area in the field. The breather cap is easily recharged with desiccant by removal of the top. 
     These and many other modifications of the present invention will be readily apparent to one skilled in the art from the claims when read in conjunction with the foregoing specification. It should be understood that the foregoing description of preferred embodiments is illustrative only, and that many modifications may be made without departing from the spirit of the invention as defined in the claims when accorded a full range of equivalents.