Pumps – Condition responsive control of pump drive motor – Responsive to pump lubricant – sealant – or coolant condition
Reexamination Certificate
1999-12-13
2001-08-21
Tyler, Cheryl J (Department: 3746)
Pumps
Condition responsive control of pump drive motor
Responsive to pump lubricant, sealant, or coolant condition
C417S063000, C340S619000, C062S129000, C062S193000, C073S293000
Reexamination Certificate
active
06276901
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention.
The present invention relates to devices for sensing the level of oil in oil sumps in hermetic refrigeration and air conditioning compressors, such as scroll, reciprocating or rotary types, and more particularly to devices for optically inspecting and automatically sensing the level of oil in sumps. One aspect of the present invention relates to sight glass type devices attached to the housing of a compressor for allowing a person to visually examine the interior of the compressor from outside the compressor housing to determine the level of oil in an oil sump or to examine the surface of oil in a sump. Another aspect of the present invention relates to automatic sensing devices that optically sense the presence or level of oil in an oil sump and perform some desired function, such as alarm or service indication or compressor shut down, in the event the oil level becomes critically low.
2. Description of the related art.
The most common form of oil level sensing device utilized today and in the past in hermetic compressors is the mechanical float switch. A float is supported by oil in the sump of a compressor and with the oil at an acceptable level the switch maintains contact between a power source and the compressor. Should the oil, and the float supported thereby, drop below a threshold level, then the switch interrupts the power supply to the compressor and thereby terminates operation. A problem associated with magnetic float switches is that they generally utilize a magnetic reed switch which attracts metallic debris that binds the float switch and causes the device to become inoperable resulting in unnecessary compressor shut down or the loss of compressor protection. This type of device is wholly mounted internal the compressor housing requiring costly compressor disassembly to replace a malfunctioning switch.
Sight glass instruments have been incorporated in hermetic compressors to permit visual inspection of the level or presence of oil in a sump. Such sight glass instruments require an operator to periodically examine the compressor to verify that an acceptable level of oil is present in the sump. A problem with such sight glass instruments is that usually compressors are mounted in the interior of an outer housing of other devices, such as refrigerators, air conditioners, automobiles, etc., and, even if positioned most favorably, are difficult to examine and may require some disassembly. Another problem with such devices is that in the event of sudden catastrophic loss of oil in a sump, no advance warning is given and damage occurs without the opportunity for remedial measures.
Automatic oil level sensing devices are known which are generally mounted wholly in the interior of a compressor housing and electrically connected to the compressor power source via electrical leads which extend from the interior of the housing to the outside of the housing through a hermetic outlet in the housing. Typically, the leads are connected to the power source external of the compressor housing. When the sensor determines that the level of oil in the sump has dropped below a critical threshold level, the sensor, via switching contacts, relay contacts, TTL logic, etc., automatically interrupts the delivery of power to the compressor and operation is terminated. One problem with such known sensors is that the only way to verify the existence of a fault condition is to disassemble the compressor, no visual inspection is provided.
Often it is the sensor that has failed and has erroneously terminated compressor operation when in fact a sufficient level of oil is present in the sump. Again, the only way to determine this is to disassemble the compressor unless a second device, such as a sight glass described above, is also incorporated in the compressor. However, if the sensor has in fact failed then it is still necessary to disassemble the compressor to replace the failed sensor. This is not an economically desirable option but the only other alternative is to electrically bypass the failed sensor and permit unprotected compressor operation.
A problem with externally mounted sensors is that the sensor continues to sense an acceptable oil level after having fallen off or been removed from the sight glass. This situation may lead to damage to the compressor if the oil level does become low.
SUMMARY OF THE INVENTION
The present invention provides a combination oil sight glass and optical sensor for determining the level of oil in a sump of a hermetic refrigeration compressor. An oil sight glass is disposed in the bottom portion of the housing of a compressor at approximately the lowest acceptable level of the oil in the sump. The sight glass fitting is generally hollow and is hermetically sealed to the compressor housing. The hollow sight glass has a first end portion adjacent the oil sump and an opposite second end portion which preferably extends outwardly from the side of the housing external of the compressor. A prism, or other such device, is disposed in the sight glass at a first end portion of the sight glass and is optically accessible via the hollow sight glass from outside the compressor. The prism part may be placed anywhere along the length of the sight glass fitting, but is preferably located outside the compressor housing at a position most easily viewed by a person maintaining the compressor. With the sight glass placed in the housing of a compressor, an individual may visually examine the level of oil in the sump by looking through the sight glass and prism and into the interior of the compressor.
In combination with the prism, an optical sensor is removably disposed in, on, or about the sight glass. The optical sensor, through the separate prism of the sight glass, automatically senses the level of oil in the sump and generates a signal or trips a switch or otherwise breaks contacts when the level becomes critically low or exceeds a predetermined operating range. Electrical leads extend outwardly from the optical sensor external of the compressor and are connected to the electrical connections of the compressor or other devices so as to achieve a desired function.
For example, the leads of the optical sensor, which may be a combination sensor and switch, may be placed in series with the compressor power source, directly or via the contacts of a relay, to automatically terminate compressor operation in the event a critically low oil level is sensed. This prevents the compressor from becoming damaged due to insufficient lubrication. Alternatively, the leads of the sensor may be connected to a compressor controller, an alarming device, or some electronic protection circuit, for automatically generating a fault indication alarm upon the occurrence of a predetermined condition. The alarm, which may take the form of a flashing light, a horn, a remote indication, etc., gains the attention of an operator who may then visually verify the existence of a fault condition via the sight glass by removing the optical sensor and looking through the sight glass and prism and into the interior of the compressor housing. The signal generated by the sensor may be input to a facility management control system to provide enhanced maintenance capabilities and reporting.
In this manner, the present invention provides an automatic sensing device which may be removed from the compressor from outside of the compressor and which has electrical leads that may be disconnected from the compressor from outside the compressor. Accordingly, the present invention provides a simplified method of replacing a failed sensor without disassembling the compressor. The present invention further provides an integral sight glass that permits visual examination of the oil level in the sump to confirm a low oil level fault condition as sensed by the optical sensor.
The sight glass and sensor combination of the present invention may be used in reciprocating compressors, scroll compressors, and rotary compressors, such as disclosed in U.S. Pat. Nos. 5,266,015, 5,306
Farr James B.
Herrick Kent B.
Baker & Daniels
Tecumseh Products Company
Tyler Cheryl J
LandOfFree
Combination sight glass and sump oil level sensor for a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Combination sight glass and sump oil level sensor for a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Combination sight glass and sump oil level sensor for a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2528445