Breather with independent inlet/outlet flow paths

The present invention provides an apparatus and method for filtering fluid in a breather assembly and providing uncontaminated fluid to a reservoir. The breather allows in-take fluid traveling through a first flow path to be filtered before entering the reservoir through a first directional valve. The breather also allows exhaust fluid traveling through a second flow path, separate from the first flow path, to exit through a second directional valve.

FIELD OF INVENTION

The present invention relates generally to fluid filtration, and more particularly to a breather for fluid filtration in a fluid system.

BACKGROUND

Certain hydraulic systems, such as those found in mobile fluid power applications, include a tank or reservoir that receives and stores hydraulic fluid. These hydraulic systems often create pressures and vacuums within the tank or reservoir during use. Breather vents are typically provided in the tank to ensure that uncontaminated air is provided into the system and that the proper pressures are maintained for efficient and safe operation of the system. These vents allow air to enter the tank or reservoir when the pressure is low, and allow air to be expelled from the tank or reservoir when the pressure is high.

As can be appreciated, such vents are subject to degradation and wear over time. A blocked or inoperable vent can prevent the proper escape or introduction of gasses and air into a tank during operation. In addition, vent gases can include oil vapor, which raise environmental and cleanliness issues if allowed to escape freely. Likewise, ambient air entering the tank through a vent can include particles or liquid that can mix with and contaminate the hydraulic fluid.

Further, when a breather becomes saturated with reservoir vapor, the system must work harder in order to receive fluid. This reduces the efficiency of the system and can lead to an increased pressure drop in the system. The greater the pressure drop in the system, the greater the likelihood that the system will be starved, resulting in cavitation. Additionally, leaks can occur resulting in hydraulic fluid escaping to the surrounding areas of system.

SUMMARY OF INVENTION

The present invention provides an apparatus and method for filtering fluid in a breather assembly and providing uncontaminated fluid to and from a reservoir. The breather allows in-take fluid traveling through a first flow path to be filtered before entering the reservoir through a first directional valve. The breather also allows exhaust fluid traveling through a second flow path, separate from the first flow path, to exit through a second directional valve. Accordingly, the apparatus and method can balance the pressures in the reservoir and filter fluid such that filtration capabilities are increased, oil exhaust is reduced, and the hydraulic system is better protected.

More particularly, included is a breather apparatus for use with a reservoir, the breather apparatus providing for the flow of uncontaminated fluid to and from the reservoir along separate flow paths. The apparatus may include a housing having an inlet for receiving fluid, an outlet for expelling fluid, and a port for fluidic communication with a reservoir. The housing encloses a first directional valve and a second directional valve for regulating fluid flow to and from the reservoir, a filtration/separation device disposed in a first flow path between the inlet and the port for filtering the fluid received at the inlet, and a second flow path between the port and the outlet, wherein the first flow path is separate from the second flow path.

In another embodiment, the housing may further include a liquid/particulate separation device disposed in the second flow path between the port and the outlet for filtering fluid expelled from the reservoir. In particular, the liquid/particulate separation device disposed in the second flow path may include a coalescing media.

In another embodiment, the first and second directional valves may be configured in reverse orientation. The apparatus may include a wall that divides a chamber in the housing into the first and the second flow paths. In particular, the wall may include a plate that divides the chamber into the flow paths. In still another embodiment, the first and second directional valves may be concentric. Additionally, the first directional valve may be disposed in a body of the second directional valve. Further, the second directional valve may include a movable piston responsive to pressure in the reservoir. Still further, the piston may be spring-biased and the piston may be disposed in the housing against a seal.

The filtration/separation device disposed in the first flow path and the liquid/particulate separation device disposed in the second flow path may be concentrically arranged in the housing. Additionally, the liquid/particulate separation device disposed in the second flow path may include a coalescing polyurethane foam. Further, the filtration/separation device disposed in the first flow path may filter the fluid received at the inlet for contaminates and liquid and the liquid/particulate separation device disposed in the second flow path may coalesce fluid from the fluid expelled from the reservoir. The fluid coalesced in the liquid/particulate separation device disposed in the second flow path may be returned to the reservoir via a drain. The breather apparatus may be in combination with the reservoir, with the breather having its port in combination with a port of the reservoir.

Moreover, the present invention provides a method for filtering fluid in a breather where the breather has an inlet and outlet, a filtration/separation device and a liquid/particulate separation device, at least a first and second directional valve, and a first flow path separate from a second flow path. The method includes receiving fluid in a reservoir via the first flow path to provide fluid in the reservoir, wherein fluid enters the inlet, is filtered in the filtration/separation device, and enters the reservoir through the first directional valve. The method also includes expelling fluid from the reservoir via the second flow path when there is a pressure build up in the reservoir, wherein fluid exits the reservoir through the second directional valve, is coalesced in the liquid/particulate separation device, and exits the outlet.

Receiving fluid may include using a directional valve disposed in a body of a movable piston, and expelling fluid may include using the movable piston. Additionally, the piston may travel against a spring allowing fluid to flow through the second flow path. Further, the piston may travel further against the spring to allow the fluid to flow through the second flow path and the first flow path. Still further, receiving and expelling fluid may also include using the first and second directional valves configured in reverse orientation.

DETAILED DESCRIPTION

Referring now to the drawings in detail, and initially toFIGS. 1,2and7, an exemplary breather assembly according to the invention is indicated generally by reference numeral10. The breather assembly10can be used in hydraulic systems, such as in industrial and mobile equipment, or in other fluid transfer systems, to provide uncontaminated fluid, in particular a gas, into the systems. The breather assembly10can also be used to prevent oil mist from escaping the systems and to provide a charge pressure on the reservoir of the systems. The breather assembly10generally includes a housing12that encloses a first directional valve14and a second directional valve22, a filtration/separation device20disposed in a first flow path, and a second flow path. These major components as well as other components of the device can be made of any suitable material, such as, for example, a polymer material such as nylon or polypropylene, metals, etc.

The first and second directional valves14and22are responsive to pressures in a reservoir11for moving the valves14and22from a closed position to an open position to permit fluid flow through the breather assembly10. When the breather10is not receiving or expelling fluid, such as air or other gas or vapor, the first and second directional valves14and22are biased toward a closed position by suitable means to prevent fluid flow below certain pressures. In one embodiment, the first directional valve14may be biased against a valve seat16toward the closed position by a spring18and the second directional valve22may be biased toward the closed position by a spring28. The springs18and28can be of varying forces to allow air to enter and exit the system based on a desired reservoir pressure.

The second directional valve22may consist of a movable piston that is responsive to pressure in the reservoir11, and may be seated by the spring28making the piston spring-biased. The first directional valve14can be disposed in the body of the movable piston, preventing air from escaping the assembly10when the movable piston is in a closed position seated against seal30. The second directional valve22can have a lip seal24integrally formed with the valve22that prevents air from entering the breather10through outlet48and also prevents air expelled from the reservoir11from entering the first flow path. As shown, the first and second directional valves14and22are concentric, although it should be appreciated that other configurations are possible, such as a side by side configuration described in detail below.

Referring now to the filtration/separation device20, the device20may be of any suitable type for filtering particulates and/or separating liquid from the air. In a preferred embodiment the filtration/separation device20may be a filtration device such as paper, glass, a melt blown filtration device, etc., although it will be appreciated that other types of filtration/separations devices can be used. Along with the filtration/separation device20, also enclosed in the housing12is a liquid/particulate separation device26disposed in the second flow path, the second flow path being separate from the first flow path. The liquid/particulate separation device26may be of any suitable type for separating a liquid and/or filtering particulates from the air passing through the device26. In a preferred embodiment, the liquid/particulate separation device26may be a coalescing media, filtration device, tortuous path, or any other way of separating a liquid droplet or mist from a gaseous stream or causing a change in the direction of a gas. The devices20and26can separate particulates out of the air to maintain air quality in the reservoir11, prevent contamination of fluid in the reservoir11, and separate fluid out of the air to promote cleanliness of the surrounding environment.

As mentioned above, the filtration/separation device20may be disposed in the first flow path, but may also be disposed in both the first and second flow paths. It should be noted that although the filtration/separation device20may be disposed in both the first and second flow paths, the flow paths would remain separate from one anther. Separating the flow paths ensures that the filtration/separation device20is not exposed to oil mist in the reservoir11, which would increase the pressure drop across the filtration/separation device20. By preventing pressure drops across the filtration/separation device20, the system is not starved, thereby preventing cavitation. Separating the flow paths also prevents reverse flow to the filtration/separation device20and/or liquid/particulate separation device26that would adversely affect the filtration capabilities of the devices. Further, separating the flow paths allows for increased filtration efficiency, reduced oil exhaust, and protection of the system.

Referring again toFIG. 1, to form the housing12, a cap32and a base36are provided, which may be removably coupled to one another by locking members34on the cap32that lock the cap32to openings38in the base36. For example, the locking members34may be resilient tabs that are snap fit into the openings38. In one embodiment, the openings38that the locking members34couple to, can also act as the inlet46. The cap32may be removably coupled to the base36by other suitable means, however, such as by clamps, fasteners, adhesives, ultrasonic welding, etc. The base36can include a port44, or be coupled to the port44, for making fluidic communication with the reservoir11. The port44is provided with a threaded portion to secure the breather10to the reservoir11, although the breather10may be secured to the reservoir11by other suitable means such as by fasteners, clamps, etc. The port44may be coupled to the reservoir11by the threads, coupled to a hose that is coupled to the reservoir11, etc. An opening is provided in the base36leading to the port44, wherein a seal30can be disposed that seals the second directional valve22with the opening in the base36to prevent air leakage in the breather10. The seal30may be of any suitable type such as a bellows seal, o-ring, etc. Although the housing12is shown as including the cap32and the base36, the housing12may be formed as one part or as multiple parts in varying configurations. An exploded view of the breather assembly10is shown inFIG. 7, which provides an example of how the parts of the assembly10communicate.

Referring again toFIG. 2, an inlet46for receiving air and an outlet48for expelling air are shown concentrically configured in the housing12. The inlet46and outlet48are disposed in the base36of the breather10, although it should be noted that the inlet46and outlet48can be located in various locations on the breather assembly10and are not limited to being concentrically configured in the housing12. The filtration/separation device20can be disposed in the first flow path between the inlet46and the port44, and the liquid/particulate separation device26can be disposed in the second flow path between the port44and the outlet48. The devices filtration/separation device20and the liquid/particulate separation device26may also be concentrically configured in the housing12, but are not limited to such a configuration.

Referring now toFIG. 3, illustrated is a condition of the breather assembly10when intake flow is supplied to the reservoir11. When a system, such as a hydraulic system, requires air due to the pressure in the system, the system can receive air through the breather assembly10. When this occurs, the first directional valve14, which can be a direct acting poppet valve, a movable piston, etc., opens to allow air to flow from outside the breather10into the reservoir11. Preferably, the pressure at which the valve14operates is low because the higher the operation pressure the greater the chance that the system will be starved of air resulting in cavitation.

More specifically, air enters the breather assembly10through the inlet46when the system requires air. The air passes through the first flow path into the filtration/separation device20where particulates, liquid, and contaminates can be separated from the air. Depending on the desired application, the filtration/separation device20can have different efficiency ratings to determine the extent of the filtration required. The air then continues to flow through the first flow path toward the first directional valve14that is in an open position, flows through the first directional valve14, and into the port44. The air then travels from the port44into the reservoir11. Once the requisite amount of air has reached the reservoir11, the valve14will close preventing any more air from entering the system.

Referring now toFIG. 4, illustrated is a condition of the breather assembly10when exhaust flow exits from the reservoir11. When a system needs to expel air due to the pressure in the system, the system will expel air in the reservoir11through the breather assembly10. When this occurs, the second directional valve22, which can be a direct acting poppet valve, a movable piston, etc., opens to allow air to flow from the reservoir11to the breather10and ultimately to the atmosphere. The pressure at which the valve22operates can be varied based on the type of system for which the breather10is being used.

More specifically, when the pressure builds up in the reservoir11, air is directed toward the breather assembly10. The air enters the breather10through the port44. The air then moves the second directional valve22from the closed position to the open position, which remains sealed in the housing12by the lip seal24, allowing the air to flow into the second flow path and out the outlet48. If the second directional valve22is a movable piston, the piston is moved up, compressing the spring28that biases the second directional valve22toward its closed position at normal pressure. After the air exits the second directional valve22, it can pass through the liquid/particulate separation device26before exiting the breather10. The liquid/particulate separation device26can be a coalescing media, such as a coalescing polyurethane foam, a tortuous path, etc. The liquid/particulate separation device26can separate a fluid, such as oil, from the air, allowing for reduced oil exhaust from the breather10. Once the requisite amount of air has exited the breather10, the second directional valve22closes preventing any more air from exiting the reservoir11. If the liquid/particulate separation device26includes a coalescing foam, the foam material can be configured to expand to fill any voids between the foam and the piston.

When the second directional valve22returns to its closed position, it can compress the liquid/particulate separation device26forcing the oil coalesced from the air back into the reservoir11via drain40. For example, if a coalescing polyurethane foam is used as the liquid/particulate separation device26, when the second directional valve22returns to its closed position, it will compress the foam forcing the oil toward the drain40below the foam leading to the port44. The oil will travel from the drain40into the port44, and then back to the reservoir11thereby saving oil as well as preventing oil exhaust.

Referring now toFIG. 5, illustrated is a condition of the breather assembly10when relief exhaust flow exits the breather10. Generally, the pressure in a reservoir11is low enough that normal operation of the breather10prevents damage in the reservoir11. In some extreme instances however, the normal exhaust flow does not allow air to exit the reservoir11quickly enough to prevent damage in known breathers. To eliminate the risk of damage, the breather10has a fail-safe relief exhaust condition. During relief exhaust, when air is traveling from the reservoir11to the port44, the fail-safe relief exhaust condition allows the second directional valve22to travel further than normal. When the second directional valve22travels further than normal, the air is allowed to exit the breather assembly10through both the outlet48and the inlet46. The air causes the second direction valve22to travel further against the spring28allowing air to flow into the first and second flow paths and out the inlet46and outlet48, respectively. Guides42are provided on the base36to ensure that the second directional valve22remains seated in its position during relief exhaust.

Turning now toFIGS. 6 and 8, another embodiment of the breather assembly according to the invention is indicated generally by reference numeral60. The breather assembly60can be used to provide uncontaminated fluid, in particular a gas, into a system, and can also be used to prevent oil mist from escaping a system and to provide a charge pressure on a reservoir of the system. The breather assembly60generally includes a housing62that encloses a first directional valve64and a second directional valve72, a filtration/separation device70disposed in a first flow path, and a second flow path. These major components as well as other components of the device can be made of any suitable material, such as, for example, a polymer material such as nylon or polypropylene, metals, etc.

The first and second directional valves64and72are responsive to pressures in a reservoir61for moving the valves64and72from a closed position to an open position to permit fluid flow through the breather assembly10. When the breather60is not receiving and expelling fluid, such as air or other gas or vapor, the first and second directional valves64and72are biased toward a closed position by suitable means to prevent fluid flow below certain pressures. The first directional valve64may be biased against a valve seat66toward the closed position by a spring68and the second directional valve72may be biased against a valve seat74toward the closed position by a spring76. The springs68and76can be of varying forces to allow air to enter and exit the system based on a desired reservoir pressure. As shown, the first and second directional valves64and72are disposed in the housing62in a side by side configuration in a reverse orientation, although it should be appreciated that other configurations are possible, such as the valves64and72being disposed in the housing62in a horizontal configuration.

Referring now to the filtration/separation device70, the device70may be of any suitable type for filtering particulates and/or separating liquid from the air. In a preferred embodiment the filtration/separation device70may be a filtration device such as paper, glass, a melt blown filtration device, etc., although it will be appreciated that other types of filtration/separations devices can be used. Along with the filtration/separation device70, also enclosed in the housing62is a liquid/particulate separation device78disposed in the second flow path, the second flow path being separate from the first flow path. The liquid/particulate separation device78may be of any suitable type for separating a liquid and/or filtering particulates from the air passing through the device78. In a preferred embodiment, the liquid/particulate separation device78may be a filtration device, coalescing media, tortuous path, or any other way of separating a liquid droplet or mist from a gaseous stream or causing a change in the direction of a gas. The devices70and78can separate particulates out of the air to maintain air quality in the reservoir61, prevent contamination of fluid in the reservoir61, and separate fluid out of the air to promote cleanliness of the surrounding environment.

Also included in the housing62is a valve plate80that includes a wall82separating the first and second flow paths. The wall82, which can be, for example, a plate, divides a chamber in the housing62into the first and second flow paths. The wall82ensures that the air entering and exiting the breather60is separate to so the filtration/separation device70is not exposed to oil mist in the reservoir61, which would increase the pressure drop across the filtration/separation device70. Separating the flow paths also prevents reverse flow to the filtration/separation device70and/or liquid/particulate separation device78that would adversely affect the filtration capabilities of the devices. Further, separating the flow paths allows for increased filtration efficiency, reduced oil exhaust, and protection of the system. In one embodiment, the breather60could be divided on either side of the wall82and then separately mounted to the reservoir61.

To form the housing62, a cap84and a base88are provided, which may be removably coupled to one another by slots86in the cap84that couple to pins90on the base88. The cap84, however, may be removably coupled to the base88by other suitable means, such as by clamps, fasteners, adhesives, ultrasonic welding, etc. The base88can include a port92, or be coupled to the port92, for making fluidic communication with the reservoir61. The port92is provided with a threaded portion to secure the breather60to the reservoir61, although the breather60may be secured to the reservoir61by other suitable means such as by fasteners, clamps, etc. The port92may be coupled to the reservoir61by the threads, coupled to a hose that is coupled to the reservoir61, etc. Although the housing62is shown as including the cap84and the base88, the housing62may be formed as one part or as multiple parts of varying configurations. An exploded view of the breather assembly60is provided inFIG. 8, which provides an example of how the parts of the assembly60communicate.

With further reference toFIG. 6, the housing62further includes an inlet94for receiving air and an outlet96for expelling air. As shown, the inlet94and outlet96are disposed on the sides of housing60, although it should be noted that the inlet94and outlet96can be located in various other locations on the breather assembly60, such as the top or the bottom of the breather60. The filtration/separation device70can be disposed in the first flow path between the inlet94and the port92, and the liquid/particulate separation device78can be disposed in the second flow path between the port92and the outlet96. The filtration/separation device devices70and the liquid/particulate separation device78can be configured with one device on each side of the wall82.

Referring now to the air in-take function of the breather60, when the system requires air due to the pressure level in the system, the system can receive air through the breather assembly60. When this occurs, the first directional valve64, which can be a direct acting poppet valve, a movable piston, etc., opens to allow air to flow from outside the breather60into the reservoir61. More specifically, when air enters the breather assembly60through the inlet94when the system requires air, the air passes through the first flow path into the filtration/separation device70where particulates, liquid, and contaminates are separated from the air. The air then continues to flow through the first flow path toward the first directional valve64that is in an open position, flows through the first directional valve64, and into the port92. The air then travels from the port92into the reservoir61. Once the requisite amount of air has reached the reservoir61, the first directional valve64will close preventing any more air from entering the reservoir61.

Referring now to the air exhaust function of the breather60, when the system needs to expel air due to high pressure in the system, the reservoir61will expel the air through the breather assembly60. When this occurs, the second directional valve72, which can be a direct acting poppet valve, a movable piston, etc., opens to allow air to flow from the reservoir61to the breather60and ultimately to the atmosphere. More specifically, when the pressure builds up in the reservoir61, air is directed toward the breather assembly60. The air enters the breather60through the port92and the second directional valve72is forced open, allowing the air to flow into the second flow path and out the outlet96. After the air exits the second directional valve72, it can pass through a liquid/particulate separation device78before exiting the breather60. The liquid/particulate separation device78can be a coalescing media, such as a coalescing polyurethane foam, a tortuous path, etc. and can separate a fluid, such as oil, from the air, allowing for reduced oil exhaust from the breather60. Once the requisite amount of air has exited the breather60, the second directional valve72will close preventing any more air from exiting the reservoir61.

Additionally, the in-take and exhaust functions, as described above, can be accomplished by using two separate breather assemblies. One breather assembly can include an inlet, a filtration/separation device, and an inlet directional valve configured to allow air into the reservoir. The second breather assembly can include an outlet, a liquid/particulate separation device, and an outlet directional valve configured to allow air to exit the reservoir. When the pressure in the reservoir is low, air is received at the inlet, is filtered in the filtration/separation device, and passes through the inlet directional valve configured in an open position. When the pressure in the reservoir is high, air exits the outlet directional valve configured in an open position, passes through a liquid/particulate separation device to coalesce oil from the air, and exits the breather assembly through the outlet. Separating the breathers provides another way of ensuring that the flow paths remain separate while the in-take and exhaust functions are performed.