Abstract:
A method and apparatus for providing steam for a test chamber is provided. The apparatus includes a heating element contained within a vessel which is fluid communication with an exterior reservoir wherein the heating element provides heat to generate steam from the water entering the vessel from the reservoir. The method for generating steam includes providing a chamber configured to contain a fluid insetting water into the chamber from a reservoir external from the chamber, controlling an amount of water inlet into the reservoir substantially equalizing the water level in the reservoir with the water level in the chamber. The method also includes heating the water in the chamber to turn at least some of the water into steam and venting at least some of the steam out of the chamber.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to steam generators. More particularly, the present invention relates to steam generators for use in test ovens and other industrial test chambers. 
   BACKGROUND OF THE INVENTION 
   Simulation test chambers are chambers designed to replicate certain environmental conditions. Objects are placed in the chambers and are evaluated to see how well the object performs under certain conditions. A test chamber may be refrigerated to cold temperatures or may be heated to certain high temperatures. Along with the temperature, humidity is also controlled to see how an object performs under various humid conditions. 
   In order to provide humidity for a test chamber, a steam generator is often used. In some steam generators, steam is generated by applying water to a heating element. The heating element boils the water and generates steam. Not supplying enough water to the heating element can cause a multitude of problems, including not generating the proper amount of steam and also other problems associated with overheating the heating element. 
   Other problems associated with current steam generators are that valves and other moving parts which may contribute to the control and/or operation of the steam generator may be located in hard to access areas. Locating moving parts that need servicing in hard to access areas may increase the difficulty of servicing and/or manufacturing the steam generator. Other problems with some known steam generators are that they have complex designs which result in high manufacturing costs. 
   Another problem associated with some steam generators is that they are hard to clean and service. Additionally, they may not easily allow water to be drained from them in order to flush sediment and other types of build-up that occur within the steam generator. 
   Accordingly, it is desirable to provide a steam generator and method of generating steam that uses a steam generator of a simplified design and is less expensive to manufacture that prior art generators. It is desirable to provide a method and apparatus for generating steam that locates the valves and other moving parts in easy to access locations to simplify service of the steam generator. It is also desirable to provide a method and apparatus for generating steam that provides a steam generator that allows for simplified cleaning and flushing the system to remove sediment and other types of buildup. 
   SUMMARY OF THE INVENTION 
   The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments provides a steam generator of a simplified design that locates the valves and other moving parts associated with a steam generator in easy to access location and that allows for simplified cleaning and flushing the system to remove sediment and other types of buildup. 
   In accordance with one embodiment of the present invention, a steam generator is provided. The steam generator includes a housing, a tubular vessel located within the housing, a heating element located within the tubular vessel, a water inlet configured to allow water to enter the tubular vessel, and a steam outlet configured to outlet steam from the tubular vessel and housing. 
   In accordance with another embodiment of the present invention, a steam generator is provided. The steam generator includes a housing, a steam chamber located within the housing, a heating element located within the steam chamber, a water inlet configured to allow water to enter the steam chamber, a steam outlet configured to outlet steam from the steam chamber and housing. The steam generator also includes a vessel located external to the steam chamber having an interior reservoir in fluid communication with the steam chamber such that a liquid level in the reservoir and a liquid level in the steam chamber will seek to achieve substantially the same level, and a valve associated with the vessel configured to regulate a liquid flow from an external source into the reservoir to achieve a desired liquid level in the reservoir. 
   In accordance with yet another embodiment of the present invention, a steam generator is provided. The steam generator includes means for containing a fluid, means for converting water to steam located in the containing means, means for inletting water into the containing means located on the containing means, means for outletting a fluid from the containing means located on the containing means and means for storing water located outside the containing means in fluid communication with the containing means and configured to store water at a level approximately equal to a level of water in the storing means. 
   In accordance with still another embodiment of the present invention, a method of generating steam is provided. The method includes the steps of providing a chamber configured to contain a fluid, inletting water into the chamber from a reservoir external from the chamber, controlling an amount of water let into the reservoir, substantially equalizing a water level in the reservoir with a water level in the chamber, heating the water in the chamber to turn at least some of the water into steam, and venting at least some of the steam out of the chamber. 
   There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
   In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
   As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of simplified schematic of a steam generator according to a preferred embodiment of the present invention. 
       FIG. 2  is a detailed perspective view of a heating element in accordance with one embodiment of the present invention. 
       FIG. 3  is a detailed perspective view of an evaporator tube assembly portion of a steam generator. 
       FIG. 4  is a detailed top view of a steam generator. 
       FIG. 5  is a detailed side view of a steam generator. 
       FIG. 6  is a detailed bottom view of a steam generator. 
       FIG. 7  is a detailed end view of a steam generator. 
       FIG. 8  is a detailed, perspective view of a steam generator. 
   

   DETAILED DESCRIPTION 
   The invention will now be described with reference to the drawing figures in which like reference numerals refer to like parts throughout. An embodiment in accordance with the present invention provides a steam generator having a tubular evaporator that is easily removed from the steam generator. Water is inlet to the evaporator where a heating element heats the water to steam. The steam is then vented out of the evaporator and steam generator. The valves for controlling water flow and other moving parts associated with the steam generator are located in a side box that is easily accessed. The easy access features provide, among other things, ease of maintenance. 
   It is understood that the term water as used herein is not limited to pure H 2 O only, but includes water and impurities often found in tap water and other water sources. The term water includes water having any trace impurities. 
   Turning now to the drawings, an embodiment of the present inventive apparatus is illustrated in  FIG. 1 .  FIG. 1  is a simplified schematic view of a steam generator  10 , in accordance with a preferred embodiment of the present invention. The steam generator  10  has a housing  12 . On one end of the housing  12  is a port  14  which allows the steam vessel  16  (also referred to as an evaporator tube) to be inserted into the housing  12 . Exterior to the housing  12  is a box housing  18 . The box housing  18  houses a water reservoir  20  and water level float valve  22 . The water level float valve  22  permits water to enter into the reservoir  20  through a reservoir inlet  24  (see  FIG. 8 ), which receives water from an external water source. The float valve  22  permits water to enter into the water reservoir  20  until the water level in the reservoir  20  achieves a certain predetermined level. Once the water level is in the reservoir  20  reaches the predetermined level, the float valve  22  will shut off the water flow from the inlet  24 . 
   The water reservoir  20  is in fluid communication with the interior of the steam vessel  16  through pipes  26 ,  28  and  30 . The water level within the water reservoir  20  will, in some embodiments of the present invention, seek to equalize with the water level within the steam vessel  16 . The piping system for the steam generator  10  includes, at least in part, main pipe  28 , the reservoir outlet pipe  26 , a steam vessel inlet pipe  30 , and an overflow pipe  32 . Pipes  26 ,  30  and  32  are all in fluid communication with the main pipe  28 . A drain valve  34 , is located at a low point in the piping system and separates main pipe  28  from drain pipe  36 . The drain valve  34  permits water to be drained from the piping system to a drain pipe  36  which can be connected to an outside drainage system in order to remove sediment and other types of buildup that may occur within the piping system. 
   A steam outlet  38  is located on the housing  12  and is in fluid communication with the interior of the steam vessel  16 . The steam outlet  38  permits the steam generated within the steam vessel  16  to be exited from the steam vessel  16  and out of the steam generator  10 . An overflow pipe  32  connects the steam outlet  38 , to the reservoir  20  to provide a relief in case of an overpressure condition within the steam vessel  16  due to a clogged steam line and unvented chamber or some other problem. 
     FIG. 2  is a detailed perspective view of an immersion heater associated with the steam generator  10 . The immersion heater  40  includes an immersible heating element  42  that is submerged in water and boils the surrounding water to generate steam. The immersion heater  40  is connected to an end plate  44  by bolts  46  (shown in  FIG. 3 ). Other types of fasting means may be use in accordance with the invention. Extending through the end plate  44  are electrical plugs  47  which communicate with an external electrical system which activates the heating element  42 . The heating element  42  in some embodiments of the invention is preferably a 1,500 watt heating element. 
   Attached to the heating element  42  is a thermostat  50 . As shown in  FIG. 2 , the thermostat  50  is connected to the top of the heating element  42 , preferably by stainless steel clips  52 . Some embodiments of the invention will use several more clips than shown in  FIG. 2 . The thermostat  50  monitors the temperature of the heating element  42 . The thermostat  50  is attached to the top of the heating element  42  because if the water level in the steam vessel  16  should drop, the top of the heating element  42  will be exposed above the water level first and therefore will be the most likely portion of the heating element to overheat. The thermostat  50  is operatively connected to the heating element  42  so that when the heating element  42  achieves an unacceptably high temperature, the thermostat  50  will shut off power or turn off the heating element  42 . 
   The thermostat  50  is an automatically setting type and automatically allows the heating element  42  to turn back on when the temperature of the heating element  42  achieves an acceptable temperature. In a preferred embodiment of the present invention, the thermostat  50  is set to trigger the turnoff of the heating element  42  when the heating element  42  achieves a temperature slightly above the boiling point of water. 
   The thermostat  50  flows through the end plate  44  through a capillary tube  54  which goes through a compression fitting  56  which is configured to not allow steam to escape through the path through the end plate made followed by the thermostat  50 . On the end plate  44  are bolt holes  48  which permit the mounting of the immersion heater  40 . In other embodiments of the invention, the immersion heater  40  may be mounted by other suitable means. 
     FIG. 3  is a perspective view of the steam vessel  16  also known as the evaporator tube  16 . The evaporator tube  16  includes an evaporator tube housing  58  which is preferably a generally tubular shape. At one end of the tube is a plate  60 . A steam vent pipe  62  is connected to the plate  60  and is put in fluid communication with the interior of the evaporator tube  16 . Through the steam vent pipe  62 , steam generated within the evaporator tube  16  exits the steam generator tube  58  and out of the steam generator  10 . 
   The water inlet  64  allows water to flow through the inlet pipe  30  through the plate  60  into the tube housing  58 . The evaporator tube housing  58  is open on the other end and has a flange  66  with holes  68  in it to allow bolts  46  to extend through the flange  66  and through the holes  48  in the end plate  44  shown in  FIG. 2 . Nuts are attached to the bolts  46  and connect the immersion heater  40  with the flange  66 . 
     FIG. 4  is the detailed top view of steam generator  10 . The exterior box housing  18  is attached to the steam generator housing  12  by mounting brackets  70  held in place with screws  72 . Other embodiments of the invention may include attaching the exterior box housing  18  to the steam generator housing  12  by other suitable means. 
     FIG. 5  is a detailed side view of the steam generator  10 . The exterior box housing  18  has a lid  74  which is removable and provides access to the valves and other components within the box housing  18 . The lid  74  is held onto the box housing  18  by lid screws  76 . Other embodiments of the invention may include a hinged box housing lid  74  or other types of fasteners that attach the lid  74  to the box housing  18 . 
   Optionally, contained within the box housing  18  (as shown in  FIG. 5 ) is a valve  78 . This optional valve  78  is an electronic float sensor. In some embodiments of the invention, the valve  78  may be used as a redundant heater element safety to shut off the heater element in the water level is too low. In addition, the valve  78  may be used as a switch to turn on an external water pump when the water level gets too low. In some embodiments of the invention, this valve  78  is an electronic GEM (G.E.M.) valve. Some embodiments of the invention will use the valve  78  in addition to the mechanical float valve  22 , other embodiments may not use the valve  78  but still use the mechanical float valve  22  shown in  FIGS. 1 and 8  to regulate water entering the box housing  18 . 
   Water exits the box housing  18  by an exit pipe  26  which attaches to the main pipe  28 . The housing exit pipe  26  is in fluid communication with the steam vessel inlet pipe  30  via the main pipe  28 . Because water can flow freely between the interior of the box housing  18  and the interior of the evaporator tube  16 , the water level contained within the box housing  18  and the water level contained within the evaporator tube  16  will seek to equalize and achieve a common level. Therefore, adjusting the height of the box housing  18  achieves a desired fluid level within the evaporator tube  16 . 
   Once the water is turned to steam within the steam evaporator tube  16 , the steam it may exit by the steam vent pipe  62 . Attached to the steam vent pipe  62  is an overflow pipe  32  which is attached to a top portion of the steam vent pipe  62  and provides an overflow in case steam or water need to escape the evaporator tube  16 . The overflow pipe  32  puts the vent pipe  62  in fluid communication with the main pipe  28 . 
   A reservoir overflow pipe  80  is also shown in  FIG. 5  and puts the reservoir  20  contained in the box housing  18  within fluid communication with the drain pipe  36 . At the end of drain pipe  36  is a fitting  82  which permits the drain pipe  36  to be attached to a drainage system. The drain pipe  36  is downstream from the valve  34  and unlike the main pipe  28  that can be blocked by valve  34 , the drain pipe  36  has free access to exit the steam generator  10 . 
   A support bracket  84  supports the steam generator housing  12  and provides a means for mounting the steam generator  10  to a desired mounting surface. In the embodiment of the invention shown in  FIG. 5 , the mounting bracket  84  is attached to a bottom portion of the steam generator housing  12 . In other embodiments of the invention, the mounting brackets  84  may be mounted to top side or end portions of the steam generator housing  12 . 
     FIG. 6  is a detailed bottom view of the steam generator  10  showing the exterior box housing  18  attached to the steam generator housing  12 . 
     FIG. 7  is a detailed end view of the steam generator  10 . The exterior box housing  18  is shown with a lid  74  and the lid screw  76  attaching the lid  74  to the box housing  18 . Also shown is the reservoir inlet  24  which permits water to be inlet into the box housing  18 . Also shown is the outlet  86  from the box housing to which the box housing overflow pipe  80  is attached. The outlet  86  is mounted at a height selected in order to allow the steam generator  10  to work properly without causing the reservoir  20  contained within the box housing  18  to overflow. 
     FIG. 8  is a detailed perspective view of the steam generator  10  mounted on the mounting brackets  84 . The steam generator  10  includes insulation sides  88 , a dense board  90  and insulation top  92 , which, in combination, provide insulating properties to the steam generator  10  to reduce the amount of heat the heating element  42  must provide in order to generate steam. 
     FIG. 8  also shows the float valve assembly  22  contained within the box housing  18  and the water inlet  24  to the box housing  18 . 
   An O-ring  94 , which may be made from silicone, provides a seal between the end plate  44  and the flange  66 , when the immersion heater  40  is installed within the evaporator tube  16 . 
   A steel grounding stud  96  provided on the housing  12  of the steam generator  10 . The grounding stud  96  provides a ground to which electric components, such as the optional GEM switch  78  and/or the electric heating element  42  may be grounded. The grounding stud  96  is connected to a grounding wire connected to ground. In some embodiments of the invention, the grounding wire connected to the grounding stud  96  is separate from the main ground associated with the chamber in which the steam generator  10  is placed. 
   Although an example of the steam generator is shown and described herein for use in test chambers, a steam generator in accordance with the invention can be used in any setting where steam and/or humidity is desired. 
   While the description herein has been directed primarily to water and steam, the invention can be applied to other fluids capable of achieving a gas and liquid form. For example other fluids may be used if desired, to test objects in environments comprising gases other than steam if gases other than steam are desired to be generated. 
   The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.