Patent Application
20070264135
The present disclosure relates generally to air compressors and more specifically to a drain valve for an air compressor.
An air compressor, for example, two-stage air compressors include a first low pressure compression stage connected through an inter-cooling stage through high pressure compression stage whose output is provided through an after cooling stage to an air reservoir. Any condensation is generally removed at the air reservoir as indicated, for example, in FIG. 1 of U.S. Pat. No. 6,027,311 and U.S. Pat. No. 4,453,893. Each of the compressor stages produces a pressure dew point that is higher than atmospheric dew point. Condensation occurs when the output of the cooler drops temperature below the pressure dew point. If the condensation is not removed at temperatures above freezing, the moist air will cause problems in the elements after the cooler. This is particularly critical in the inter-cooling stage wherein the air is input into a second compressor stage. If condensation is not removed at or below freezing, the moisture can potentially block the exit of the cooling stages. This is also true at the output of the final or after cooling stage.
One suggestion, as described in U.S. Pat. No. 6,952,932, is to bypass the after cooling stage such that gases are used to heat the cooled gases when ambient temperatures is at or below freezing, and are used downstream from the after cooling stage when moisture freezes in the after cooling stage.
It is well-known in the multistage air compressors to have unloading valves at the output of the inter-cooling stage as illustrated by U.S. Pat. No. 6,287,085 and at the output of the after cooling stage as illustrated in U.S. Pat. No. 4,819,123.
The present air compressor system includes an inlet connected to a compression stage, a cooling stage having an inlet connected to an outlet of the compression stage and having an outlet passage; a drain valve having a liquid inlet in and adjacent a bottom of the outlet passage of the cooling stage to drain condensation when opened; and a controller controlling the compression stage and the drain valve.
A liquid inlet of the drain valve is at the lowest point in the outlet passage. The liquid inlet may be an end of a siphon tube in the outlet passage of the cooling stage. The drain valve includes an air port connected to the outlet passage of the cooling stage whereby air passing from the air port to the drain through the open drain valve educes liquid from the outlet passage of the cooling stage through the siphon. The air port is higher than an end of the siphon connected to the outlet passage of the cooling stage.
The system may include first and second compression stages and the cooling stage is the inter-cooling stage. The cooling stage is connected to an outlet of the first compression stage and the outlet passage of the cooling stage is connected to an inlet of the second compression stage. The drain valve may be connected between the inter-cooling stage and the second compression stage. Alternatively, the drain valve may be connected to the after cooling stage which is connected to the outlet passage of the second compression stage.
A drain valve assembly for an air compressor system includes a housing having a passage extending between a first port and a second port; a valve chamber having a liquid inlet in and adjacent a bottom of the passage and having a drain outlet; a valve seat in the valve chamber between the drain outlet and the liquid inlet; and a valve element responsive to an input signal to cover and uncover the valve seat.
The liquid inlet may be an end of a siphon tube in the passage. The valve chamber includes an air port connected to the passage whereby air passing from the air port to the drain outlet through the open valve seat educes liquid from the passage through the siphon. The air port is higher than an end of the siphon connected to the passage. The valve seat is higher than the liquid inlet.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
A piston compressor of the prior art is illustrated in
The cooling system 16 for the two-stage compressor includes an inter-cooling stage 20 and an after cooling stage 22. The inter-cooling stage 20 has an inlet (not shown) connected by pipe 24 from the outlet of piston cylinders 14b and 14c to the inter-cooling stage 20. Outlet 25 of inter-cooling stage 20 is connected via outlet passage 26 to the inlet of the second stage piston cylinder 14a. The output of the second stage piston cylinder 14a is connected via pipe 28 to an inlet of the after cooling stage 22.
As previously discussed, condensation will collect in the inter-cooling stage outlet passage 26, as well as exiting from outlet 17 of the after cooling stage 22. This collected condensation will freeze at lower temperatures and impede the operation of the compressor.
A drain valve assembly 30, illustrated in
By connecting port 34 of passage 38 at the lower outlet 27 of the inter-cooling stage, the bottom 37 of passage 38, which is an extension of the outlet passage of the inter-cooling stage 20 outlet, is below the inlet to the compressor stage 14a. Thus, this part of the passage 38 is the natural collection point for all condensation in the inter-cooling stage 20 outlet passage. The area adjacent the drain valve 40 is lower than the ports 34 and 36 to form a well to collect the condensation.
The drain valve 40 includes a valve chamber 42 which includes a valve seat 44 mounted therein. Valve element 46 covers and uncovers the valve seat 44 to open and close the drain valve. An air inlet 48 connects the passage 38 to the valve chamber 42. A liquid inlet 50 is at the end of a tube 52 which is also connected to the valve chamber 42. Tube 52 forms a siphon as will be described. The end or the liquid inlet 50 is in the passage 38 and adjacent the bottom 39 of the passage 38. It should also be noted that the liquid inlet 50 is below the height of the valve seat 44. The air inlet 48 is above the valve seat 44. Alternatively, the valve seat 44 may be below the liquid inlet 50 and the tube 52 being replaced with a passage in the wall of the passage 38 connecting the passage 38 to the valve chamber 42. A drain sleeve 54 is threaded into opening 56 of the housing 38 below the valve seat 44.
Since the air outlet of the inter-cooling stage is pressurized, when the valve 40 is open, the air will rush through air inlet 48 and through the open valve seat 44. Such an action induces or creates a vacuum to siphon the liquid resting on the bottom 39 of passage 38 up through the siphon tube 52 and into the valve chamber 42 where it exists the open valve 40. When the valve 40 is closed with valve element 42 on valve seat 44, the pressure in chamber 40 is the same as the pressure in the passage 38 and has none or little effect on moving any of the condensate liquid on the floor 39 of passage 38 into the valve chamber 42.
Although a pneumatic control of the drain valve 40 is illustrated, a solenoid control may be provided. The valve element 46 is controlled by a signal from controller 92 shown in
Piston 60 is mounted in piston chambers 62, which is separated from the valve chamber 42 by sleeve 64. Valve element 46 is mounted to the piston 60 by a fastener 66. A control port 68 in housing 38 provides the input signal to the valve chamber 62 via passage 65 in sleeve 64 to the bottom of the piston chamber 62 below piston 60 to raise it against a spring 70 to open the valve 40. The spring 70 biases the piston 60 to the down position closing the drain valve 40.
As shown in
A drain valve with its housing 32 adapted for connection at the outlet of the after cooling stage 22 is illustrated in
The operation of the drain valves 30 in both embodiments is controlled by the controller 92 which also controls the compressor by controlling drive 12 as shown in
Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. Two drain valves 30 may be connected to the outlet of each cooling stage, 20, 22 or at the outlet of only one cooling stage. The scope of the present invention is to be limited only by the terms of the appended claims.
