Abstract:
A humidistat including an air inlet defining a beginning of an airflow path through the humidistat, a humidity sensor for enabling measurement of the humidity of air flowing along the airflow path, a baffle, a heat source for heating air along a portion of the airflow path, the baffle and the heat source cooperating to define two zones in the humidistat, and an air outlet defining an end of the airflow path. During operation of the humidistat, the air temperature is higher in one zone than in the other zone, and the higher air temperature zone is downstream from the lower air temperature zone in the airflow path.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to an improved humidistat for regulating the humidity inside a piano. 
   Changes in relative humidity adversely affects pianos, particularly due to swelling and contraction of the piano soundboard. In geographical zones where humidity swings are substantial, such as, for example, between 20% and 75% relative humidity, pianos which do not have humidity control apparatus must be tuned often, e.g., every few weeks, in order for the pianos to perform properly. In addition, the swelling and contraction of the soundboard and other wood parts over time will result in a deterioration of the structural integrity of the entire piano. Thus it is desirable to maintain stable relative humidity inside the piano notwithstanding swings in relative humidity outside the piano. To accomplish this, readings of the relative humidity in very close proximity to the piano soundboard must be as accurate as possible. 
   Dampp-Chaser Electronics Corporation (“Dampp-Chaser”), assignee of the present invention, is the leading manufacturer of piano humidity control systems. Dampp-Chaser manufactures piano humidifiers, dehumidifiers, and humidistats which are used to control the relative humidity inside the piano. Examples of Dampp-Chaser&#39;s humidity control systems are set forth in its U.S. Pat. Nos. 4,150,372, 4,423,658, 5,903,223, and 6,133,519. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram of a rear vertical cross-sectional view of a prior art piano humidistat shown in spatial relation to a soundboard of a grand piano; 
       FIG. 2  is a schematic diagram of a rear vertical cross-sectional view of an improved piano humidistat according to an embodiment of the invention, shown in spatial relation to a soundboard of a grand piano; and 
       FIG. 3  is a line graph comparing the respective humidity control performances of the prior art piano humidistat shown in  FIG. 1  and the improved piano humidistat shown in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A prior art piano humidistat manufactured by the assignee of the present invention, Dampp-Chaser Electronics Corporation, is shown broadly in  FIG. 1  at reference numeral  10  in relation to a piano soundboard  11 . The prior art humidistat  10  includes a humidity sensor housing  12 , a humidity sensor  13  within the humidity sensor housing  12 , a printed circuit board  14 , electrical power outlets  15  for an associated dehumidifier and humidifier (not shown), and various power and utility cords  16 . The prior art humidistat  10  also defines a plurality of openings  20  through which air may enter and exit the humidistat  10 . In addition, a safety baffle  21  is situated in close proximity to the openings  20  in the humidistat  10  nearest the printed circuit board  14  in order to prevent a curious user from being shocked by inserting electrically conductive materials through the openings  20  nearest the printed circuit board  14  and contacting live electrical elements such as those that are powered on the printed circuit board  14  during humidistat  10  operation. 
   For optimal performance of a piano humidistat, the humidity sensor therein should continually be exposed to the air closest in proximity to the piano soundboard, as it is the relative humidity of this particular air that provides the most accurate measure of the relative humidity of the soundboard itself. Positive air flow from the area closest in proximity to the soundboard toward the humidity sensor of the humidistat is desired in order for the humidity sensor to be exposed to the most accurate representation of the current relative humidity of the air closest in proximity to the piano soundboard. Close proximity of the humidity sensor and the soundboard is desired for the same reason. 
   One method of bringing about positive air flow in a humidistat is through creation of a “chimney effect” within the humidistat. Such an effect may be created by defining two zones within the humidistat and causing a first zone to maintain a higher air temperature than a second zone during humidistat operation. However, in order to avoid the relative air temperature equalization that will naturally occur over time between the first and second zones, at least partial physical separation of the zones is required. In addition, the zones must be situated such that air flow between them is sufficiently constricted and directed between and within the zones to stimulate air flow from the lower air temperature zone into the higher air temperature zone. If these preconditions are met, during humidistat operation the lower temperature air will flow substantially downward through the lower air temperature zone toward the higher air temperature zone, where it will be heated. The heated air will be drawn further into the higher air temperature zone as it rises out of the humidistat. This air flow will cause a partial vacuum in the lower air temperature zone that will in turn be filled by air flowing into the lower air temperature zone from outside the humidistat. In this way, the desired positive air flow through the humidistat may be achieved. 
   Turning again to  FIG. 1 , the heat naturally generated by electrical circuitry (not shown) on the printed circuit board  14  during operation of the prior art humidistat  10  may be helpful toward achieving the desired chimney effect within the humidistat. However, the prior art humidistat  10  does not define zones having materially different air temperatures, and therefore the heat radiating from the electrical circuitry on the printed circuit board  14  during humidistat operation is spread and dissipated relatively evenly throughout the prior art humidistat  10 , preventing any substantial positive air flow through the prior art humidistat  10 . In any event, whatever positive air flow does occur within the prior art humidistat  10  as a result of the heat from the electrical circuitry on the printed circuit board  14  actually occurs in a direction opposite to the desired direction, that is, toward the soundboard  11  rather than away from the soundboard  11 , as shown by arrows and dotted lines marked “AF” that indicate the airflow path. In addition, the humidity sensor  13  in the prior art humidistat  10  is physically separated from the soundboard  11  by the humidistat  10  itself. 
   Turning now to  FIG. 2 , an improved piano humidistat  30  in accordance with an embodiment of the invention is illustrated. This improved humidistat  30  is larger than the prior art humidistat  10  ( FIG. 1 ) and better accomplishes the above objectives. A baffle  31  is included within the humidistat  30  to help define first and second zones  32 ,  33  within the humidistat. The baffle  31  could be oriented at any one of a variety of different angles and/or shaped as any one of a variety of different curves as long as air is able to flow from the first zone  32  into the second zone  33  during humidistat operation. Additionally, the baffle  31  could extend the full internal height of the humidistat and include openings to allow airflow through the baffle  31 . It should be noted that a safety baffle such that shown in the prior art humidistat ( FIG. 1  at  21 ) is unnecessary in the improved humidistat in light of the electrical components of the improved humidistat being oriented away from any openings into the humidistat. 
   During humidistat operation, electrical circuitry (not shown) on a printed circuit board  34  oriented in the second zone  33  heats the air in the humidistat such that the air temperature in the second zone  33  is generally higher than the air temperature in the first zone  32 . Air enters the lower air temperature zone  32  through an air inlet  40  in the humidistat  30 , and having a relatively low ambient temperature, falls substantially downward through the lower air temperature zone  32  as shown by arrows and dotted lines marked “AF” that indicate the airflow path through the humidistat. As it enters the humidistat  30 , the air encounters and is sensed by the humidistat sensor  42 , which therefore enables measurement of the relative humidity of the air in very close proximity to the piano soundboard  11 , one of the desired results described above. As it continues to fall through the lower air temperature zone  32 , the air nears an end  35  of the baffle  31 , where it begins to be heated by heat that radiates from the electrical circuitry (not shown) on the printed circuit board  34  in the higher air temperature zone  33  when the printed circuit board  34  is electrically powered during humidistat  30  operation. As shown by the airflow path indicated with the arrows and dotted lines “AF”, the heated air then begins to flow substantially upward toward the printed circuit board  34 , where the air continues to increase in temperature and continues to flow substantially upward through the higher air temperature zone  33  before ultimately exiting the humidistat  30  through an air outlet  41  in the humidistat  30 . This improved configuration provides the desired positive air flow (“AF”) in the desired direction, namely, away from the soundboard  11 . 
     FIG. 3  shows a graph comparing the humidity regulation performance of the prior art humidistat  10  shown in  FIG. 1  (noted as “H 3 ” in the graph in conjunction with dotted lines with triangles thereon) and the improved humidistat  30  shown in  FIG. 2  (noted as “H 4 ” in the graph in conjunction with solid lines). For each of the two humidistats, ten readings (bottom scale of graph) of the equilibrium moisture of the soundboard (left-hand scale of graph) are shown for each of three relative humidities (noted within graph). Equilibrium soundboard moisture readings between approximately 6.6 and 6.8 are desired, as this range is consistent with those encountered in soundboards maintained in the storage facilities of most piano manufacturers. This equilibrium moisture range correlates to a range of approximately 42–46% relative air humidity around the soundboard. As can be seen from  FIG. 3 , the improved humidistat  30  (“H 4 ,” solid lines) maintains the equilibrium moisture of the soundboard in the desired 6.6 to 6.8 range far more consistently than the prior art humidistat  10  (“H 3 ,” dotted lines with triangles) across multiple readings and at varying relative air humidities. 
   An improved piano humidistat is described above. Various details of the invention may be changed without departing from its scope. Furthermore, the foregoing description of an embodiment of the invention and the best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation—the invention being defined by the claims.