Abstract:
The invention is a continuously operated condensate drain valve operating in real-time response to the presence of an electrically conductive media in the interior chamber of the condensate drain valve. The invented valve includes a valve body, a subminiature sensor embedded in the valve body and an electric control circuit electrically connected to the sensor. Because the sensor is located in the valve body and because the control circuit does not include a delay means, the invented valve can operate at an extremely high cycle rate thereby keeping the air compression system virtually condensate free. Consequently, the invented valve enables an air compressor to maintain optimal capacity and to operate at an unprecedented level of efficiency.

Description:
FIELD OF THE INVENTION 
     The present invention relates to condensate drain valves used in conjunction with apparatus for compressing air. More particularly, the invention relates to a condensate drain valve operating in response to the presence of electrically conductive media in the interior chamber of the condensate drain valve. The present invention also relates to a method for efficiently discharging condensate through a condensate drain valve. 
     BACKGROUND 
     Compressed air is a valuable energy source. When air is compressed, the moisture content of the air is released as water vapor which forms condensate. Condensate is an unwanted byproduct of air compression. Condensate occupies a portion of the volume of an air compression chamber thereby decreasing the working volume of the chamber. The more space the condensate occupies in the air compression chamber, the lower the capacity of the air compressor. Maintaining condensate at minimal levels increases the efficiency of the air compression operation. 
     Fluid transfer systems utilized in conjunction with air compressors are well known for removing condensate from the air compression chamber. One component of a fluid transfer system is a condensate drain valve. Condensate drain valves enable accumulated condensate to be periodically discharged from the air compression chamber. Although known condensate drain valves are suitable for this purpose, none of the known condensate drain valves efficiently handle the task. 
     Initially, condensate drain valves were manually operated. Recently, numerous attempts have been made to automate the operation of condensate drain valves. One type of known condensate drain valve utilizes a mechanical float system to trigger the opening of the condensate drain valve. The mechanical float system has a ball positioned in a seat. The ball has a lower density than does the condensate. Consequently, when condensate enters the interior chamber of the valve, the float rises and the condensate escapes through an orifice below the seat. After the condensate escapes, the float returns to its initial position on the seat. Known condensate drain valves that utilize mechanical float systems have numerous disadvantages. Typically, slug and scale alter the surface of the seat. This results in gas leakage when no condensate is present. Energy losses from using such condensate drain valves can range from a few hundred to several thousand dollars per year. 
     Another known type of condensate drain valve is equipped with a timer. The timer utilizes a power relay which causes an electrically operated condensate drain valve to activate. The timer is set, by a trial and error approach, to periodically open the valve. The condensate is forced out through the valve by the force of the compressed air. The timer keeps the valve open for a fixed amount of time and then causes the valve to close. Because the timer does not precisely correspond to the presence of condensate, the valve will often be open for either too little or too much time. It is estimated that a properly installed timed condensate drain valve loses approximately $1,900 per year. As these valves are often not properly installed, the average valve actually loses much more money. 
     Another known type of condensate drain valve uses an external vessel to collect condensate formed in the air compression chamber. Sensors, typically reed switches, sense the presence of condensate. When condensate is detected, the sensor causes the valve to open. After the condensate is removed, the sensor causes the valve to close. This type of condensate drain valve is complex and very expensive to manufacture. Frequently, the savings from more efficient air compression are exceeded by the high cost of using this type of condensate drain valve. 
     Solenoid operated valves are also well known. Solenoid operated valves include an electromagnetic coil assembled over a tube mounted to the body of the valve. An armature is positioned inside the tube and is used to start, stop or divert the flow of liquid or gaseous media. The armature has a spring and a spring loaded sealing disc. In operation, the sealing disc is moved against the force of the spring when the electromagnetic coil is energized thereby opening the valve. Various types of solenoid operated valves using this basic structure are known including: direct acting solenoid valves; pilot operated solenoid valves; and pilot operated with assisted lifting valves. 
     One known type of solenoid operated condensate drain valve is disclosed in U.S. Pat. No. 4,261,382 to Bridges (“the &#39;382 patent”). The solenoid operated condensate drain valve includes an electrical sensing probe inserted in a condensate drain line upstream of the valve so as to be electrically insulated from the drain line. While electrical isolation is necessary for the solenoid operated condensate drain valve to operate properly, this placement of the probe permits condensate to build-up to unnecessarily high levels thereby reducing the efficiency of the air compressor. 
     As disclosed in the &#39;382 patent, the electrical sensing probe is connected by electrical leads to an electronic circuit. The electric circuit has voltage supply leads and is connected by electrical leads to the solenoid of the valve. In operation, when the probe does not sense the presence of condensate, the electronic circuit receives the oscillating signal rather than the steady positive output from the probe. When the electric circuit receives the oscillating signal, a timing cycle is initiated during which the solenoid is de-energized and the valve is closed. Although the disclosed electric circuitry performs the intended task, it is overly complex as evidenced by the requirement that the sensor be electrically isolated from the drain line. 
     The solenoid operated condensate drain valve disclosed in the &#39;382 patent also includes a delay means for providing a desired minimum period between successive operations of the valve such that the valve remains closed for a pre-set period of time. 
     Because the condensate drain valve does not react to the presence of condensate in the interior chamber of the valve body, excessive condensate necessarily accumulates in the interior chamber of the valve body. Consequently, the efficiency of the air compressor is reduced. 
     Because of the limitations of known condensate drain valves, a need exists for a valve that can continuously minimize the amount of condensate present in the fluid transfer system of an air compressor. 
     While there are numerous methods and means for discharging condensate from an air compressor, none are known to be similar to, or to function in the manner of, the present invention. 
     SUMMARY OF THE INVENTION 
     The present invention is a solenoid operated condensate drain valve operating in real-time response to the presence of an electrically conductive media in the interior chamber of the condensate drain valve. The invented valve includes a valve body forming an interior chamber, a sensor embedded in the valve body and extending into the interior chamber and an electric control circuit electrically connected to the sensor. The sensor is preferably a subminiature sensor which is sufficiently small to allow the sensor to be embedded in the valve body. Because the sensor is located in the valve chamber and because the control circuit does not include a delay means, the invented valve can continuously discharge condensate before it accumulates excessively. Consequently, the invented valve enables an air compressor to maintain optimal capacity and to operate at an unprecedented level of efficiency. 
     Preferably, the condensate drain valve includes a two-way (on-off) solenoid valve having an input port and an output port for a liquid, gas or combination of both liquid and gas type medium to flow through. The control circuit is an open electrical circuit that uses condensate to close or complete the control circuit. When no condensate is present in the interior chamber, the control circuit is open and the condensate drain valve is in a closed position. When condensate is present in the interior chamber, the control circuit is closed and an electrical relay is activated which causes the solenoid to become energized. Consequently, the condensate drain valve is opened thereby allowing condensate to be discharged through the output port of the valve. 
     The subminiature sensor includes a tubular housing containing a pair of electrodes that are both insulated by glass. The tubular housing has a diameter of about {fraction (1/16)} inch and is made of a corrosion resistant material that is electrically conductive and is preferably made of 430 stainless steel. A first electrode is in electrical contact with the tube and a second electrode is exposed to the environment. 
     The sensor is embedded within the valve body in such a manner that the face of the sensor is positioned away from the flow of gas and/or liquid medium, for example, in the direction of the output port of the valve. As a result, the electrodes are protected by the sensor housing from damage due to the force of the flow of liquid, cavitation of the passing liquid, and blockage from particulates in the liquid. 
     The control circuit is electrically connected to the sensor embedded in the body of the condensate drain valve. The control circuit transmits an electrical signal that travels through one of the electrodes of the sensor. Preferably, the control circuit is housed in an enclosure or controller housing that is removably attached to the solenoid valve body. An electrical port provides a means for connecting a power supply to the control circuit. While the power supply requirements of the invented drain valve vary depending upon the control circuits being powered, a 12 volt AC, 1.5 mA power supply is exemplary. 
     Because the control circuit does not specifically incorporate delay means, the invented drain valve will have an extremely high cycle rate. Consequently, condensate will always be immediately drained from the interior chamber and the air compression system will operate at near optimal efficiency. 
     The controller may include a power indicator diode, a test button and a valve open indicator diode to improve the performance of the invented drain valve. 
     During operation of the air compressor, condensate will enter the interior chamber of the condensate drain valve. The control circuit remains open until an electrically conductive media, such as condensate, comes into simultaneous contact with the valve body, which is in electrical contact with the first electrode, and the second electrode. Because condensate has a greater degree of conductivity than air, the electrical signal bridges the gap between the first electrode and the second electrode thereby closing the control circuit. As a result, the closed control circuit causes the solenoid to energize thereby opening the condensate drain valve and allowing the condensate to be discharged. The condensate drain valve remains open as long as the control circuit is closed. 
     When only air is present between the sensor, the electrical signal does not pass from the first electrode to the second electrode because air does not have sufficient conductivity to permit the electrical signal to pass from the first electrode to the second electrode. Consequently, the control circuit is open, and the valve is in the closed position. 
     After the condensate has been discharged, the control circuit again opens which causes the solenoid to de-energize thereby returning the valve to the closed position. After the control circuit opens, it is immediately ready to close again when the circuit is again closed by condensate causing the electrodes to become electrically connected. 
     In an alternative embodiment of the present invention, the condensate drain valve detects and drains different types of media having different conductivities. The electric control circuit includes a resistance comparator circuit for detecting the conductivity of the different types of media. The resistance comparator circuit is electrically coupled to the sensor and is adjustable to correspond to different types of media having different conductivities. 
     Also disclosed is a method for efficiently operating a solenoid operated condensate drain valve that minimizes the level of condensate in the fluid transfer system of an air compressor. The invented method includes the step of detecting the presence of an electrically conductive media, particularly condensate, in the interior chamber with a subminiature sensor mounted in the valve body. Preferably, the sensor detects the presence of condensate by passing an electrical signal between a first electrode, or the valve body which is in electrical contact with the first electrode, and the second electrode which is electrically isolated from the first electrode and valve body. The invented method also includes the step of closing the control circuit, of which the sensor is a part, when the condensate is detected. The invented method further includes the step of energizing the solenoid of the drain valve by activating a relay switch to energize the solenoid, when the control circuit is closed. Finally, the invented method includes the step of opening the valve and discharging the condensate when the solenoid is energized. 
     The invented method also preferably includes closing the valve when condensate is no longer detected by the sensor. Thus, when the signal no longer passes between the first electrode, or the valve body which is in electrical contact with the first electrode, and the second electrode which is electrically isolated from the first electrode and valve body, the control circuit is opened. When the control circuit is opened, the relay switch is no longer activated and the solenoid of the valve is de-energized thereby closing the valve. 
     OBJECTS OF THE INVENTION 
     Accordingly, one of the objects of the present invention is to provide a condensate drain valve that is continually responsive to the presence of condensate in the interior chamber of the condensate drain valve. 
     A further, and more particular, object of the invention is to provide a solenoid operated condensate drain valve that permits the discharge of condensate when an electrically conductive media is present in the interior chamber of the condensate drain valve. 
     A further, and more particular, object of the invention is to provide a solenoid operated condensate drain valve that discharges condensate when an electrically conductive media is present in the interior chamber of the condensate drain valve and that is simple and economical to manufacture. 
     Another object of the invention is to provide a condensate drain valve that maintains the optimal capacity of an air compressor. 
     It is a further object of the present invention to provide a method for operating a condensate drain valve in a manner that minimizes the level of condensate in the fluid transfer system of an air compressor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects will become more readily apparent by referring to the following detailed description and the appended drawings in which: 
     FIG. 1 is a side view of a preferred embodiment of a controller housing and a solenoid operated condensate drain valve according to the present invention; 
     FIG. 2 is a front view of the condensate drain valve of FIG. 1; 
     FIG. 3 is a top view of the condensate drain valve taken along line  3 — 3  of FIG. 1; 
     FIG. 4 is a cross-sectional side view of a sensor according to the present invention; and 
     FIG. 5 is a diagram of an electric circuit that can be incorporated in the condensate drain valve of FIG.  1 . 
     FIG. 6 is a diagram of an alternative embodiment of the electric circuit of FIG. 5 that can be incorporated in the condensate drain valve of FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, and particularly to FIG. 1, the invented apparatus is a solenoid operated condensate drain valve, shown generally at  10 , for efficiently discharging condensate from the fluid transfer system of an air compressor. FIG. 2 is a front view of the continuously operated condensate drain valve  10  of FIG.  1 . In a preferred embodiment, the invented drain valve  10  includes a hollow valve body  12  that forms an interior chamber  14 , a sensor  16  embedded in the valve body  12  and an electric control circuit, shown generally at  18  (FIG.  5 ), electrically connected to the sensor  16  and the drain valve  10 . The sensor  16  includes a pair of electrodes for detecting a presence or accumulation of condensate in the drain valve  10 . The control circuit  18  provides an electrical signal to the sensor  16  to determine the presence of condensate in the drain valve  10  and activates the drain valve when the presence of condensate is detected. The invented drain valve  10  opens in real time response to the presence of condensate in the valve body  12 , and preferably opens instantaneously in response to a detected presence of condensate the interior chamber  14  of the valve body  12 . 
     FIG. 3 is a top view of the condensate drain valve taken along line  3 — 3  of FIG.  1 . The valve body  12  includes an input port  11  for receiving a flow of liquid and/or gas media and an output port  13  for conducting the liquid and/or gas media liquid away from the valve body  12 . The valve body  12  contains a conventional solenoid operated valve  29  (FIGS. 5 and 6) having a solenoid coil  22  (FIGS. 5 and 6) and a relay contact  24  electrically coupled to the solenoid coil  22 . When the solenoid coil  22  is energized, the valve  29  is closed, and when the solenoid coil  22  is not energized or de-energized, the valve  29  is opened. 
     FIG. 4 is a cross-sectional side view of the sensor  16 . The sensor  16  extends through the valve body  12  and into the interior chamber  14  while substantially maintaining the structural integrity of the valve body  12  and maintaining a gas-tight and liquid-tight interface with the valve body  12 . In a preferred embodiment of the present invention, the face of the sensor  16  is positioned in the valve body  12  in the general direction of the output port of the drain valve  12 . The sensor  16  is preferably a subminiature sensor and includes a pair of electrodes electrically connected to the control circuit  18 , a generally cylindrical enclosure  15  for housing the pair of electrodes and an electrical insulation  17  encompassing the pair of electrodes within the tubular enclosure  15 . 
     One of the electrodes, or a first electrode (not shown), is electrically connected to the cylindrical enclosure  15 , for example by conventional soldering or welding techniques, so that electrical signals or current are conducted between the electrode and the valve body  12 . The other electrode  21 , or a second electrode, is electrically insulated from the valve body  12  by the electrical insulation  17  and is preferably proximally positioned along the longitudinal axis defined by the cylindrical enclosure  15 . The cylindrical enclosure  15  is made of an electrically conductive material and is preferably made of 430 stainless steel. The electrical insulation  17  is preferably made of glass, but may also be made of electrically insulating ceramic material. The generally cylindrical enclosure  15  has a diameter that is smaller than ⅛ inch and preferably about {fraction (1/16)} inch. The subminiature size of the sensor  16  allows the sensor  16  to be embedded in the valve body  12 , whereas non-subminiature sized sensors are too large. 
     FIG. 5 is a diagram of the electric control circuit  18 . The control circuit  18  includes a relay coil  42  that is coupled to the sensor  16  and is housed in a controller enclosure  20  (FIGS. 1 and 2) that is removably attached to the valve body  12 . The relay coil  42  is electrically connected to the sensor  16  by a pair of electrical leads  36 . The sensor  16  is electrically connected to the control circuit  18 , as previously mentioned, to form an open electrical circuit. In a preferred embodiment, the control circuit  18  transmits an electrical signal that travels along one of the electrodes, for example, the electrical signal is transmitted by the control circuit  18  along the first electrode. When an electrically conductive media contacts the sensor  16 , current is provided to the relay coil  42  which closes the relay contact  24 . The relay coil  42  and the relay contact  24  of the solenoid operated valve together form a relay switch  42 ,  24  for energizing/de-energizing the solenoid coil  22 . When the relay contact  24  is closed, the solenoid  22  energizes and the drain valve  10  opens. 
     The control circuit  18  is electrically coupled to a power converter, shown generally at  27 , to provide the control circuit  18  with a pre-determined amount of electrical current and potential. The primary transformer  30  and the secondary transformer  32  convert the power input from the power supply  28  to a power level that is suitable for energizing the solenoid  22 . A port  26  (FIG. 1) is positioned on the controller enclosure  20  (FIG. 1) for connecting a conventional power supply  28  to the control circuit  18 . The power converter  27  includes a primary transformer  30  electrically coupled to the port  26  and a secondary transformer  32  electrically coupled to the primary transformer  30 . While the power supply requirements of the invented drain valve  10  vary depending upon the control circuits being powered, a 12 volt AC, 1.5 mA power supply is exemplary. 
     In operation, when an electrically conductive media, such as condensate, is present in the interior chamber  14  of the valve body  12 , the electric signal passes from one of the electrodes to the other electrode through the electrically conductive media, and the control circuit  18  is thereby closed. When the control circuit  18  is closed, the relay switch  24 ,  42  is activated thereby instantaneously energizing the solenoid  22 . As a result, the valve  29  is opened and the electrically conductive media is discharged. When the electrically conductive media is no longer present in the interior chamber  14  of the valve body  12  so that the signal can no longer pass from one electrode to the other electrode, the control circuit  18  is thereby opened. As a result, the relay switch  24 ,  42  de-activates causing the solenoid  22  to de-energize and close the valve  29 . 
     Thus configured, the invented valve  10  minimizes the amount of condensate present in the fluid transfer system attached to an air compressor by instantaneously removing the condensate once it begins to accumulate in the interior chamber  14  of the valve body  12 . The invented valve  10  is opened and closed in a real time response to the presence of condensate within the valve body  12 . No delay is incorporated in the operation of the invented drain valve  10 . 
     FIG. 6 is an exemplary control circuit of an alternative embodiment of the present invention. The control circuit, indicated generally as  18 , includes an electrical power supply  28  for providing an electrical potential or power input to the circuit  18 . The primary transformer  30  and the secondary transformer  32  convert the power input from the power supply  28  to a power level that is suitable for energizing the solenoid  22 . The control circuit  18  also includes a resistance comparator circuit  34  for determining the conductivity of different electrically conductive media. The comparator circuit  34  is electrically connected to the sensor  16  by the electrical leads  36 . A resistance setpoint  40  and the relay coil  42  complete the control circuit  18 . The resistance setpoint  40  is adjustable to match a pre-determined conductivity that is desired to be detected by the sensor  16 . The relay coil  42  is coupled to the relay contact  24  to form the relay switch  24 ,  42 . When an electrically conductive media contacts the sensor  16 , current is provided to the relay coil  42  which closes the relay switch  24 ,  42 . When the relay switch  24 ,  42  is closed, the solenoid  22  energizes and the drain valve  10  is opened. 
     In one embodiment of the present invention, the primary transformer  30  and secondary transformer  32  are housed in a power supply enclosure  19  that is removably attachable to the controller enclosure  20 . The port  26  is positioned on the power supply enclosure  19  for connecting the conventional power supply  28  to the control circuit  18 . The controller enclosure  20  houses the control circuit  18  and is removably attachable to the valve body  12 . Accordingly, the power supply enclosure  19 , the controller enclosure  20  and the valve body  12  are removable from one another to facilitate replacement of a defective component. 
     SUMMARY OF THE ACHIEVEMENT OF THE OBJECTS OF THE INVENTION 
     From the foregoing, it is readily apparent that I have invented a solenoid operated condensate drain valve that maintains the optimal capacity of an air compressor because it is continually responsive electrically conductive media in the interior chamber of the valve body. The invented condensate drain valve causes condensate to be discharged when an electrically conductive media, such as condensate, is present in the interior chamber of the condensate drain valve. The present invention provides a solenoid operated condensate drain valve that discharges condensate when an electrically conductive media is present in the interior chamber of the condensate drain valve and that is simple and economical to manufacture. I have also invented a method for efficiently operating a condensate drain valve that minimizes the level of condensate in the fluid transfer system of an air compressor. 
     It is to be understood that the foregoing description and specific embodiments are merely illustrative of the best mode of the invention and the principles thereof, and that various modifications and additions may be made to the apparatus by those skilled in the art, without departing from the spirit and scope of this invention.