Patent Application
20080050250
Referring first to
An unloader 20 causes compressor 12 to be in an unloaded state in response to a pneumatic signal being received at a signal port 22 thereof. Unloader 20 may be integrally formed as part of compressor 12 (as shown in the Figures), or may comprise a separate component. Again, since numerous such unloaders are extremely well-known in the art, the particular structure and operation of unloader 20 is not discussed herein in detail.
Air supply system 10 also includes an isolation valve 24 having an inlet port 26, an outlet port 28 and a signal port 30. Inlet port 26 of isolation valve 24 is in fluid communication with a source of inlet air (indicated by arrow A). Source of inlet air may simply be the atmosphere, or may be a turbocharger supplying air under pressure. An air filter or the like (not shown), or some other component or components may be provided if desired, without affecting the operation of the present invention. Outlet port 28 of isolation valve 24 is in fluid communication with inlet port 16 of compressor 12 via conduits 32, 34.
Isolation valve 24 allows air to flow from inlet port 26 of isolation valve 24 to outlet port 28 of isolation valve 24, and thereby allows air to flow from source of inlet air A to inlet port 16 of compressor 12, when no pneumatic signal is received at signal port 30 of isolation valve 24, and prevents air from flowing from inlet port 26 of isolation valve 24 to outlet port 28 of isolation valve 24, and thereby prevents air from flowing from source of inlet air A to inlet port 16 of compressor 12, when a pneumatic signal is received at signal port 30 of isolation valve 24. Referring more specifically to the exemplary embodiments illustrated, isolation valve 24 comprises a valve body 36 moveable, in response to a pneumatic signal being received at signal port 30 of isolation valve 24, between an open position (shown in the Figures) in which isolation valve 24 allows air to flow from inlet port 26 of isolation valve 24 to outlet port 28 of isolation valve 24 (indicated by arrow B), and thereby allows air to flow from source of inlet air A to inlet port 16 of compressor 12 via isolation valve 24 and conduits 32, 34, and a closed position (when valve body is moved downward with respect to the orientation shown in the Figures such that valve body 36 seals against valve seat 38) in which isolation valve 24 prevents air from flowing from inlet port 26 of isolation valve 24 to outlet port 28 of isolation valve 24, and thereby prevents air from flowing from source of inlet air (A) to inlet port 16 of compressor 12. Preferably, valve body 36 is biased toward the open position by a spring 40 or the like, and is moveable against the bias to the closed position when a pneumatic signal is received at signal port 30 of isolation valve 24.
Air supply system 10 also includes a governor 42 of the conventional type having an unloading port 44 in fluid communication with signal port 30 of isolation valve 24 (via conduits 46, 48) and with signal port 22 of unloader 20 (via conduits 46, 50). Governor 42 also includes an exhaust port 52 in fluid communication with a low pressure environment (such as atmosphere) and a reservoir port 54 in fluid communication with a signal outlet port 56 of a reservoir 58 via conduits 60, 62.
Signal outlet port 56 of reservoir 58 is also in fluid communication with inlet port 16 of compressor 12 via conduits 62, 64, 34. A pressure regulator 66 is disposed in fluid communication between signal outlet port 56 of reservoir 58 and inlet port 16 of compressor 12, preferably along conduit 64.
Outlet port 18 of compressor 12 is in fluid communication with an inlet port 67 of reservoir 58 via one or more conduits 68. As indicated at 70, such communication need not be direct communication, and there may be one or more components, such as an air dryer or even an entire system for regulating the exhaust side of compressor 12 (such as the system disclosed in U.S. Pat. No. 4,993,922), disposed between outlet port 18 of compressor 12 and inlet port 67 of reservoir 58. An outlet port 72 of reservoir 58 supplies compressed air (indicated by arrow C) to various other components of a brake system or some other system employing compressed air for operation.
Operation of air compressor system 10 will now be described. When compressor 12 is in its loaded pumping mode, isolation valve 24 is in its open position, and air is drawn from source of inlet air A through inlet port 26 of isolation valve 24, outlet port 28 of isolation valve, conduits 32, 34 and inlet port 16 of compressor 12 into compression chamber 14. Air compressed within compression chamber 14 then exists outlet port 18 of compressor 12 and enters inlet port 67 of reservoir 58 via conduit 68 and any intermediate components 70.
Compressed air is transmitted from reservoir 58 through signal outlet port 56 of reservoir 58, via conduits 62, 60, to reservoir port 54 of governor 42 and, via conduits 62, 64, 34 and pressure regulator 66, to inlet port 16 of compressor 12. At this point, no pneumatic signal is being transmitted from governor 42 to isolation valve 24 or unloader 20.
When the pressure within reservoir 58, and therefore at reservoir port 54 of governor, reaches a threshold level, a pneumatic signal (i.e., pressurized air) is transmitted from governor 42, through unloading port 44, in a manner known in the art, and to signal port 30 of isolation valve 24 (via conduits 46, 48) and at the same time to signal port 22 of unloader 20 (via conduits 46, 50). The pneumatic signal received by unloader 20 causes compressor 12 to switch to its unloaded mode of operation, while the signal received by isolation valve 24 causes isolation valve 24 to switch to its closed position, thereby cutting off communication between inlet port 16 of compressor 12 and source of inlet air A.
At the same time, pressurized air continues to be transmitted from reservoir 58 through signal outlet port 56 of reservoir 58, via conduits 62, 64, 34 and via pressure regulator 66, to inlet port 16 of compressor 12, thereby causing pressure to be maintained on the inlet side of compressor 12. Pressure regulator 66 preferably regulates a pressure the pneumatic signal such that the pressurized air supplied by reservoir 58 to inlet port 16 of compressor 12 has a pressure about equal to a pressure of air in the crankcase of compressor 12.
Pressure regulator 66 also ensures that the valve body 36 of isolation valve 24 does not become unseated before such is desired. More specifically, if the pressure within conduit 32 were equal to the pressure within conduit 48, the combined force of the pressure at outlet port 28 of isolation valve 24 plus the force exerted by spring 40 would be higher than the force of the pressure at signal port 30 of isolation valve 24, such that the valve body 36 may be moved away from its closed position. By ensuring that pressure regulator 66 reduces the pressure of the pneumatic signal sufficiently, this problem can be avoided. Of course, the problem could also be avoided by disposing a check valve or the like within conduit 32 or outlet 28 of isolation valve 24.
Referring now to
More specifically, signal outlet port 56 of reservoir 58 is in direct fluid communication with only reservoir port 54 of governor 42 (via conduit 74), and not with inlet port 16 of compressor 12. Unloading port 44 of governor 42 is in fluid communication with signal port 30 of isolation valve 24 (via conduits 46, 48), with signal port 22 of unloader 20 (via conduits 46, 74, 76) and with inlet port 16 of compressor 12 (via conduits 46, 74, 78, 34 and pressure regulator 66).
Operation of air compressor system 10′ will now be described. When compressor 12 is in its loaded pumping mode, isolation valve 24 is in its open position, and air is drawn from source of inlet air A through inlet port 26 of isolation valve 24, outlet port 28 of isolation valve, conduits 32, 34 and inlet port 16 of compressor 12 into compression chamber 14. Air compressed within compression chamber 14 then exists outlet port 18 of compressor 12 and enters inlet port 67 of reservoir 58 via conduit 68 and any intermediate components 70.
Compressed air is transmitted from reservoir 58 through signal outlet port 56 of reservoir 58, via conduit 74, to reservoir port 54 of governor 42. At this point, no pneumatic signal is being transmitted from governor 42 to isolation valve 24, unloader 20 or inlet port 16 of compressor 12.
When the pressure within reservoir 58, and therefore at reservoir port 54 of governor, reaches a threshold level, a pneumatic signal (i.e., pressurized air) is transmitted from governor 42, through unloading port 44, in a manner known in the art, and to signal port 30 of isolation valve 24 (via conduits 46, 48), to signal port 22 of unloader 20 (via conduits 46, 74, 76), and to inlet port 16 of compressor 12 (via conduits 46, 74, 78, 34 and pressure regulator 66). The pneumatic signal received by unloader 20 causes compressor 12 to switch to its unloaded mode of operation, while the signal received by isolation valve 24 causes isolation valve to switch to its closed position, thereby cutting off communication between inlet port 16 of compressor 12 and source of inlet air A.
At the same time, pressure is maintained on the inlet side of compressor 12 due to the pressurized air being transmitted from unloading port 44 of governor 42 and to inlet port 16 of compressor 12 (via conduits 46, 74, 78, 34 and pressure regulator 66). Pressure regulator 66 preferably regulates a pressure the pneumatic signal such that the pressurized air supplied by governor 42 to inlet port 16 of compressor 12 has a pressure about equal to a pressure of air in the crankcase of compressor 12. Pressure regulator 66 also ensures that the valve body 36 of isolation valve 24 does not become unseated before such is desired in the manner described above.
As should be appreciated from the above detailed description of system operation, air supply system 10, since pressurized air is supplied directly from reservoir 58 to compressor 12 without passing through governor 42, supplies pressurized air to the compressor whether the compressor 12 is in the loaded or unloaded mode. However, since, in air supply system 10′, pressurized air is supplied to compressor 12 via unloading port 44 of governor 42, pressurized air is only supplied while compressor 12 is in its unloaded state.
The present invention, therefore, provides 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.
Although the invention has been described with reference to a particular arrangement of parts, features and the like, these are not intended to exhaust all possible arrangements or features, and indeed many other modifications and variations will be ascertainable to those of skill in the art.
