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Air supply system with reduced oil passing in compressorAir supply system with reduced oil passing in compressor description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080050250, Air supply system with reduced oil passing in compressor. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001]The present invention relates generally to air supply systems using reciprocating type air compressors and, more particularly, to compressor unloading systems usable in such air supply systems, such as might be found in air supply systems for truck air brakes and the like. BACKGROUND OF THE INVENTION [0002]It is well known in the art that in air supply systems, such as might be found in air supply systems for truck air brakes and the like, the air compressor operates in its pumping mode for only a relatively short period of time, and that it is operated in what is known as an unloaded mode for as much as approximately 70-90 percent of the time. How to unload the air compressor to save horsepower when the compressor is not pumping, without having other problems occur, has been a long standing problem in the art. [0003]Air compressors used in medium and heavy duty vehicle air supply systems, such as those found in transport trucks, passenger buses, and the like, generally involve having an air compressor directly driven by the vehicle engine and supplied with inlet air at atmospheric pressure, or, in the case of many transport trucks today, turbocharged air from the engine turbocharger via the engine air intake manifold. [0004]These air compressors generally are one, two or four cylinders in nature. The earliest attempts at internally unloading the air compressor in regard to two cylinder compressors was to simply hold the intake valves for both cylinders open and pump air back and forth between the cylinders, and this was relatively satisfactory when there was no concern with the fuel cost or the horsepower being lost. [0005]With single cylinder air compressors, the earliest unloading method simply involved holding the intake valve open so that air was pumped in and out through the compressor intake opening. [0006]In the European countries, the approach to the problem was somewhat different, and while the intake valve was left untouched, the compressor pumped all the time while the unloading function was performed external to the compressor via a separate diverted type system called an unloader valve. This method of unloading is now generally viewed as unsatisfactory because of the noise produced, and the horsepower losses incurred. Thus, design and development work focused on better ways to unload air compressors other than simply holding the intake valve open. [0007]In many cases, when the intake valve was held open on a single cylinder air compressor and the compressor was supplied with naturally aspirated air, which was common at the time, since the compressor intake was supplied with a separate air cleaner, pumping back and forth through the air cleaner in many cases destroyed the air cleaner, or reduced its efficiency so it would not perform for the purpose for which it was intended. [0008]This caused some truck manufacturers to switch to a system supplied with turbocharged inlet air from the engine turbocharger to avoid the air cleaner problems and assure a clean inlet air supply, but it was then found that when unloading in the conventional way, by holding the intake valve open, the faster the engine was running, the denser the air, and the more horsepower was lost due to the unloading. Thus, the search continued for a satisfactory solution to the problem. [0009]A clutched compressor was developed, but was not felt to be the answer to the horsepower loss problem because the compressor shaft normally runs through the compressor and often drives other accessories, such as the power steering, or engine fuel pump, and it was not satisfactory to have the power steering and other items nonfunctional for the time the compressor was unloaded. Also, the clutched compressor would substantially increase the cost of the air supply system, and this was not satisfactory. Thus, not much progress was made in developing a more efficient compressor unloading system, and simply holding the intake valve open to allow unloading either to atmosphere, or the engine turbocharger, was the accepted way of unloading the air compressor for some time. [0010]More recent attempts have been made to solve the aforementioned longstanding problems in the prior art, and provide a more efficient compressor unloading system for use with heavy duty air supply systems. One such attempt resulted in U.S. Pat. No. 4,993,992 to Lauterbach et al., in which is disclosed a system that employs either mechanical or pneumatic means to effectively prevent the intake and exhaust valves, which are generally of the pressure operated spring type, from operating during the unloading cycle. In the disclosed system, a mechanical means stops the spring-type, pressure operated intake valve from operating by blocking the compressor intake, while a pressure operated means, including an isolation valve for use with air dryer equipped air systems, effectively stops the exhaust valve of the air compressor from operating, thereby creating an "air spring." [0011]However, while the system disclosed in U.S. Pat. No. 4,993,992 does provide advantages over previously known systems, it suffers from disadvantages of its own. One such disadvantage was that, while the system employs elevated pressure at the exhaust side of the compressor in order to prevent the exhaust valve from operating, the pressure at the intake side remains relatively low. Thus, a pressure differential is formed across the pistons of the compressor, with higher pressure being maintained on the exhaust side, and lower pressure being maintained on the intake side. This pressure differential, in turn, leads to increased levels of oil passing, which, as is known, leads to further complications within the system. [0012]What is desired, therefore, is an air supply system which is efficient in operation and economical to manufacture, which reduces the horsepower used by air compressors in their unloaded mode as compared to traditional systems, which is automatically actuated in the unloading mode, which causes relatively equalized pressure to be maintained on both sides of the compressor pistons, and which results in reduced levels of oil passing around the compressor piston rings when the compressor is in its unloading mode. SUMMARY OF THE INVENTION [0013]Accordingly, it is an object of the present invention to provide an air supply system which is efficient in operation and economical to manufacture. [0014]Another object of the present invention is to provide an air supply system having the above characteristics and which reduces the horsepower used by air compressors in their unloaded mode as compared to traditional systems. [0015]A further object of the present invention is to provide an air supply system having the above characteristics and which is automatically actuated in the unloading mode. [0016]Still another object of the present invention is to provide an air supply system having the above characteristics and which causes relatively equalized pressure to be maintained on both sides of the compressor pistons. [0017]Yet a further object of the present invention is to provide an air supply system having the above characteristics and which results in reduced levels of oil passing around the compressor piston rings when the compressor is in its unloading mode. [0018]These and other objects of the present invention are achieved, in accordance with one embodiment of the present invention, by provision of an air supply system including a compressor having a compression chamber, an inlet port through which air flows into the compression chamber and an outlet port through which air exits the compression chamber, an unloader which causes the compressor to be in an unloaded state in response to a pneumatic signal received at a signal port, and an isolation valve. The isolation valve has an inlet port, an outlet port and a signal port, the inlet port of the isolation valve being in fluid communication with a source of inlet air, and the outlet port of the isolation valve being in fluid communication with the inlet port of the compressor. The isolation valve allows air to flow from the inlet port of the isolation valve to the outlet port of the isolation valve, and thereby allows air to flow from the source of inlet air to the inlet port of the compressor, when no pneumatic signal is received at the signal port of the isolation valve, and prevents air from flowing from the inlet port of the isolation valve to the outlet port of the isolation valve, and thereby prevents air from flowing from the source of inlet air to the inlet port of the compressor, when a pneumatic signal is received at the signal port of the isolation valve. The air supply system also includes a governor having an unloading port in fluid communication with the signal port of the isolation valve and with the signal port of the unloader, the governor supplying a pneumatic signal to the signal port of the isolation valve and the signal port of the unloader when a desired system air pressure is maintained, and a source of pressurized air supplying pressurized air to the inlet port of the compressor at least when the pneumatic signal is received by the isolation valve. [0019]In some embodiments, the pressurized air supplied by the source of pressurized air to the inlet port of the compressor has a pressure about equal to a pressure of air in the crankcase of the compressor. In some embodiments, the source of pressurized air comprises an air reservoir in fluid communication with the inlet port of the compressor. In certain of these embodiments, the air supply system further includes a pressure regulator in fluid communication between the air reservoir and the inlet port of the compressor, the pressure regulator regulating a pressure of air supplied by the reservoir such that the pressurized air supplied by the reservoir to the inlet port of the compressor has a pressure about equal to a pressure of air a in the crankcase of the compressor. [0020]In some embodiments, the unloading port of the governor is in fluid communication with the inlet port of the compressor, such that the source of pressurized air comprises the unloading port of the governor. In certain of these embodiments, the air supply system further includes a pressure regulator in fluid communication between the unloading port of the governor and the inlet port of the compressor, the pressure regulator regulating a pressure of air supplied by the unloading port of the governor such that the pressurized air supplied by the unloading port of the governor to the inlet port of the compressor has a pressure about equal to a pressure of air in the crankcase of the compressor. In certain embodiments, the governor further comprises a reservoir port, and the air supply system further includes a reservoir having a port in fluid communication with the reservoir port of the governor. [0021]In some embodiments, the isolation valve comprises a valve body moveable, in response to the pneumatic signal received at the signal port of the isolation valve, between an open position in which the isolation valve allows air to flow from the inlet port of the isolation valve to the outlet port of the isolation valve, and thereby allows air to flow from the source of inlet air to the inlet port of the compressor, and a closed position in which the isolation valve prevents air from flowing from the inlet port of the isolation valve to the outlet port of the isolation valve, and thereby prevents air from flowing from the source of inlet air to the inlet port of the compressor. In certain of these embodiments, the valve body is biased toward the open position, and is moveable against the bias to the closed position when the pneumatic signal is received at the signal port of the isolation valve. Continue reading about Air supply system with reduced oil passing in compressor... Full patent description for Air supply system with reduced oil passing in compressor Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Air supply system with reduced oil passing in compressor patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Air supply system with reduced oil passing in compressor or other areas of interest. ### Previous Patent Application: Progressive vortex pump Next Patent Application: Reciprocatory fluid pump Industry Class: Pumps ### FreshPatents.com Support Thank you for viewing the Air supply system with reduced oil passing in compressor patent info. 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