Air compressor with oil pump inlet strainer bypass valve

An air compressor with oil pump inlet strainer bypass features, including a bypass valve assembly in fluid communication with the air compressor crankcase to provide lubricating oil to the dynamic compressor components, or simply to the air compressor. The bypass valve assembly includes a valve housing defining an interior chamber and an oil strainer screen engaged with the valve housing to filter the lubricating oil entering the interior chamber. A bypass valve is in fluid communication with the interior chamber and includes a valve body having a bypass port and an indicator port. An optional suction tube is connected to the bypass port on the valve body. An indicator assembly is connected to the indicator port on the valve body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of air compressors adapted for use on rail vehicles and, more particularly, to avoiding air compressor failure due to oil pump inlet strainer obstructions.

2. Description of Related Art

Normally, a pneumatic system is provided for a rail vehicle by which the brakes of the rail vehicle are operated. An air compressor is used to supply compressed air to one or more pneumatic units associated with the rail vehicle involved in the operation of the brakes. The air compressor usually consists of a driving unit, such as an electric motor, and a compressor unit, which typically consists of several piston-cylinder arrangements that are driven by a crankshaft. The crankshaft is driven by the driving unit and includes connecting rods to convert the rotating movement of the driving unit into linear movement for each piston to supply compressed air to the downstream units. Screw-type air compressors are also generally known in the field for this purpose and are also included within the scope of the present invention. Furthermore, air compressor units for use on rail vehicles may have a single-stage or a multi-stage construction with at least one low-pressure stage and one high-pressure stage. The air compressors used in the rail vehicle field may be subjected to continuous operation or to frequent on-and-off operation. In either mode of operation, friction during operation of the compressor leads to high heat development. As a result, air compressors predominantly used in the rail vehicle field use oil lubrication to ensure sufficient lubrication and cooling during operation.

Air compressors used on rail vehicles typically have an oil strainer located at the inlet to the air compressor oil pump which is designed to filter large particles, such as carbon debris. The oil strainer prevents entry of particles and other debris into the oil pump and from being passed through the moving components of the air compressor. Over time, the strainer screen becomes increasingly obstructed by the particles and debris being filtered. As the degree of obstruction increases, air compressor damage can occur due to a decrease in oil flow and pressure reaching the moving components. This damage can eventually result in air compressor failure. If the strainer screen becomes 100% obstructed, air compressor failure will occur unless the strainer screen itself fails, allowing oil to pass to the oil pump inlet. One known prior art solution to avoid strainer screen obstruction issues is to entirely remove or omit the strainer screen, but this solution also eliminates the benefits of pre-filtering the lubricating oil used in the air compressor.

SUMMARY OF THE INVENTION

The present invention is generally directed to avoiding air compressor failure due to oil pump inlet strainer obstructions by providing an oil pump inlet strainer bypass valve assembly for the air compressor. The bypass valve assembly desirably includes an indicator system or assembly that indicates when the bypass valve assembly is in a bypass mode and is, therefore, in need of maintenance. The bypass valve assembly, as described in detail herein, addresses the problem of air compressor failure due to oil pump inlet strainer obstructions while maintaining the benefits of pre-filtering the lubricating oil used in the air compressor using a strainer screen, and generally allows for improved maintenance practices. The indicator system or assembly of the bypass valve assembly, as described in detail herein, may be embodied to provide a visual indication of when maintenance is required. Further, the bypass valve assembly provides improved lubrication in cold temperature environments.

In one embodiment described in detail herein, an air compressor with oil pump inlet strainer bypass features is disclosed that includes a bypass valve assembly in fluid communication with the air compressor crankcase to provide lubricating oil to the dynamic compressor components or, simply, to the compressor. The bypass valve assembly includes a valve housing defining an interior chamber and an oil strainer screen engaged with the valve housing to filter the lubricating oil entering the interior chamber. A bypass valve is in fluid communication with the interior chamber and includes a valve body having a bypass port and an indicator port. A suction tube is connected to the bypass port on the valve body. An indicator assembly is connected to the indicator port on the valve body. The bypass valve opens to permit lubricating oil to enter the interior chamber via the suction tube without passing through the oil strainer screen when a predetermined differential pressure across the oil strainer screen is reached.

The valve housing comprises an outlet port for connection to an oil pump. The bypass valve may be supported in an opening in the valve housing leading to the interior chamber. The bypass valve may comprise a spring-biased ball valve. The oil strainer screen may be seated in a strainer port opening in the valve housing.

The indicator assembly comprises an indicator tube connected with the indicator port on the valve body, and a condition indicator in fluid communication with the indicator tube. The condition indicator may be a mechanical or an electronic device. The condition indicator may include a display to indicate that the bypass valve is open and permitting lubricating oil to enter the interior chamber via the suction tube without passing through the oil strainer screen. The condition indicator display may register a change of visual indicia to indicate that the bypass valve is open and permitting lubricating oil to enter the interior chamber via the suction tube without passing through the oil strainer screen. The condition indicator may be adapted to detect a vacuum condition in the indicator tube.

In another embodiment, a bypass valve assembly for providing lubricating oil to an air compressor is disclosed. The bypass valve assembly is in fluid communication with the air compressor crankcase to provide lubricating oil to the dynamic compressor components or, simply, to the compressor. The bypass valve assembly includes a valve housing defining an interior chamber and an oil strainer screen engaged with the valve housing to filter the lubricating oil entering the interior chamber. A bypass valve is in fluid communication with the interior chamber and includes a valve body having a bypass port and an indicator port. A suction tube is connected to the bypass port on the valve body. An indicator assembly is connected to the indicator port on the valve body. The bypass valve opens to permit lubricating oil to enter the interior chamber via the suction tube without passing through the oil strainer screen when a predetermined differential pressure across the oil strainer screen is reached.

The valve housing comprises an outlet port for connection to an oil pump. The bypass valve may be supported in an opening in the valve housing leading to the interior chamber. The bypass valve may comprise a spring-biased ball valve. The oil strainer screen may be seated in a strainer port opening in the valve housing.

The indicator assembly comprises an indicator tube connected with the indicator port on the valve body, and a condition indicator in fluid communication with the indicator tube. The condition indicator may be a mechanical or an electronic device. The condition indicator may include a display to indicate that the bypass valve is open and permitting lubricating oil to enter the interior chamber via the suction tube without passing through the oil strainer screen. The condition indicator display may register a change of visual indicia to indicate that the bypass valve is open and permitting lubricating oil to enter the interior chamber via the suction tube without passing through the oil strainer screen. The condition indicator may be adapted to detect a vacuum condition in the indicator tube.

Further details and advantages of the various embodiments described in detail herein will become clear upon reviewing the following detailed description of the preferred embodiments in conjunction with the accompanying drawing figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For purposes of the description hereinafter, spatial orientation terms, as used, shall relate to the referenced embodiment as it is oriented in the accompanying drawing figures or otherwise described in the following detailed description. However, it is to be understood that the embodiments described hereinafter may assume many alternative variations and configurations. It is also to be understood that the specific components, devices, and features illustrated in the accompanying drawing figures and described herein are simply exemplary and should not be considered as limiting.

Referring toFIGS. 1-5, a multi-cylinder air compressor1is shown which includes an oil pump inlet strainer bypass valve assembly10(hereinafter “bypass valve assembly10”) that is intended to address the issue of air compressor failure due to a fully or partially obstructed oil strainer screen. As described previously, an oil strainer screen is typically located at the inlet of an oil pump, namely, in the oil pump suction line, and functions to filter large particles and debris from the air compressor lubricating oil prior to this oil entering the oil pump. As the hours of air compressor operation increase, this oil strainer screen can become fully or partially obstructed resulting in air compressor damage and eventual failure. The bypass valve assembly10is embodied to maintain oil flow to the air compressor oil pump in the event of full or partial oil strainer screen obstruction, thereby preventing air compressor damage or failure.

The bypass valve assembly10comprises a valve housing12that is located on top of and engaged with an oil strainer screen14(hereinafter “strainer screen14”). In particular, the valve housing12defines an interior chamber16, a strainer port opening18, and an outlet port20. The strainer port opening18is configured to accept and support the strainer screen14and the strainer screen14is held in place in the strainer port opening18via a retaining ring22. A top wall24of the valve housing12defines a central opening26to accept and secure a bypass valve30to the valve housing12. The valve housing12further comprises a mounting portion28used to mount the bypass valve assembly10to the air compressor1.

The bypass valve30comprises a valve body32defining a bypass port34, an indicator port36, and a valve seat38. A ball check40is located within the valve body32and is biased into engagement against the valve seat38by a biasing spring42. The ball check40and spring42are secured within the valve body32by a valve stop44, a retaining ring46, and a locknut48. A stem portion50of the valve body32extends through the central opening26in the top wall24of the valve housing12and is secured in connection with the valve housing12by the locknut48located within the interior chamber16of the valve housing12. A sealing washer54is provided on the stem portion50so that a generally fluid-tight seal is present between the valve body32and valve housing12. A suction tube56is connected to the bypass port34on the valve body32, and an indicator system or assembly58is connected to the indicator port36on the valve body32. The suction tube56may be provided as part of the assembly10or as a part of the air compressor1. The indicator assembly58comprises a valve connector60used to connect an indicator tube62with the indicator port36on the valve body32, and a condition indicator64in fluid communication with the indicator tube62. The condition indicator64may be mounted to a panel2on the air compressor1. The condition indicator64may be a mechanical or an electronic device.

Generally, the bypass valve assembly10operates based on the differential pressure across the strainer screen14. When the differential pressure increases above a set limit, indicating that the strainer screen14is at least partially blocked or fouled with particulate matter and debris, the ball check40lifts from the valve seat38allowing lubricating oil to enter the valve housing12on the oil pump side of the strainer screen14via the bypass suction tube56. The lubricating oil is pulled from the crankcase through the suction tube56into the valve housing12and then into the inlet to the oil pump (not shown) connected to the outlet port20. The suction that is created in the valve housing12when the bypass valve30opens creates a vacuum in the indicator tube64. This vacuum is sensed, either mechanically or electronically, by the condition indicator64mounted, for example, on an access panel2which may be on a crankcase3of the air compressor1. The vacuum condition sensed by the condition indicator64may register as a change of visual indicia on the condition indicator64, such as a color change on a display66on condition indicator64, where the color changes from green to red. The bypass valve30may remain open until the differential pressure across the strainer screen14reduces below the preset limit. When the bypass valve30closes, the vacuum condition in the indicator tube64vents and the display66will change back to its original state or condition, such as returning to green from red.

Accordingly, in view of the foregoing, the bypass valve assembly10provides a way to avoid or minimize compressor damage or failure as a result of the strainer screen14becoming fully or partially obstructed. As the strainer screen14becomes increasingly obstructed, differential pressure across the strainer screen14increases. The bypass valve assembly10may be set such that the bypass valve30opens when a predetermined or preset differential pressure across the strainer screen14is reached. When the bypass valve30opens, it becomes a full-flow inlet port to the oil pump (not shown), completely bypassing the strainer screen14. In this manner, the air compressor1will not be starved of lubricating oil flow and pressure due to an obstructed strainer screen14. The bypass valve assembly10avoids air compressor failures by bypassing an obstructed or partially obstructed strainer screen14. However, when the bypass valve30opens due to obstruction, the air compressor1is in a vulnerable operating state. In this state, the air compressor1is operating without any lubricating oil filtering at the inlet to the oil pump (e.g., at outlet port20), which allows debris to be circulated with the lubricating oil through the moving components of the air compressor1. As a result, the indicator assembly58provides a way alert the user that the air compressor1is in a “bypass mode” and requires maintenance. The condition indicator64is desirably positioned on the exterior of the air compressor, such as the side cover access panel2on the crankcase. The condition indicator64includes the display66which may be a simple red/green process indicator, where the red region indicates that the bypass valve30is in bypass mode and the green region indicates the bypass valve30is closed or normal operation. While a visual indicator may be used, other warning forms may also be used such as an auditory warning that the air compressor1is in the bypass mode, or a combination of visual and auditory warnings may be provided. Moreover, the condition indicator64may be electronically linked to a remote console on the rail vehicle or other location, either directly or wirelessly, to alert a user of the bypass condition. Therefore, when there is no vacuum present in the indicator tube62, the display66is typically green and when vacuum is present the display66is typically red.

The obstruction of the strainer screen14can generally be avoided by following proper maintenance practices such as periodic inspection, cleaning, and/or replacing the strainer screen14. However, for many reasons, these practices are not always performed. Also, since the rate of obstruction may vary greatly depending on usage, environment, other maintenance practices, etc., it is often difficult to determine an adequate maintenance interval for the strainer screen14. The inclusion of the bypass valve assembly10provides an apparatus to avoid catastrophic failure when these circumstances lead to obstruction of the strainer screen14. Although the air compressor1is typically operating in a less than optimal condition when the bypass valve30is in the bypass mode, the benefit of avoiding catastrophic failure far outweighs the negative of operating, for a limited period, without proper lubricating oil filtering. Furthermore, the indicator system or assembly58provides a way to assure that the hours of operation spent in the bypass mode are limited. Generally, the bypass valve assembly10provides a “failsafe” condition so that poor maintenance practices do not result in catastrophic air compressor failures.

Furthermore, the bypass valve assembly10provides a benefit in cold temperature applications. In cold temperature applications, lubricating oil may become very thick when the air compressor1is not operating. When the air compressor1is started with cold lubricating oil, it takes more time for the more viscous lubricating oil to reach the internal components of the air compressor1. This period of lack of lubrication may result in increased wear of the moving components of the air compressor1. In these situations, the increased differential created by the thick lubricating oil being pulled through the strainer screen14results in the opening of the bypass valve30. This unobstructed oil path through the bypass suction tube56temporarily provides the air compressor1with an adequate amount of lubricating oil. Once the lubricating oil begins to circulate, the pressure differential across the strainer screen14decreases and the bypass valve30closes.

While embodiments of an air compressor including an oil pump inlet strainer bypass valve assembly for railway and like vehicles and methods of operation thereof were provided in the foregoing description, those skilled in the art may make modifications and alterations to these embodiments without departing from the scope and spirit of the invention. Accordingly, the foregoing description is intended to be illustrative rather than restrictive. The invention described hereinabove is defined by the appended claims and all changes to the invention that fall within the meaning and the range of equivalency of the claims are to be embraced within their scope.