Abstract:
The invention concerns a desiccant box for dehumidifying air, with a cylindrical outer housing ( 10 ), a lid ( 11 ) that closes the outer housing, and an inner housing ( 12 ) to accommodate desiccant ( 13 ). The lid ( 11 ) features at least one inflow opening ( 14 ) and at least one outflow opening ( 15 ), the contour of the outer housing opposite the lid being curved. Moreover, another inner housing ( 17 ) is provided which is located in the area of the contour ( 16 ) and runs approximately along this contour, this inner housing being also filled with desiccant ( 18 ), and the two inner housings ( 12  and  17 ) being connected to each other.

Description:
CROSS REFERENCE TO RELATED FOREIGN APPLICATIONS 
     This application claims priority benefit under 35 U.S.C. 119 to German Utility Patent Application number 10 2007 034 435.1, having a filing date of Jul. 20, 2007 at the German Patent Office. 
     TECHNICAL FIELD 
     The present invention relates to air drying devices and, more particularly, to a desiccant box for dehumidifying air. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a desiccant box for dehumidifying air. Germany patent DE 103 13 575 discloses a desiccant box having an inner housing that accommodates the desiccant and an outer housing with a cover lid. To fasten the inner housing and compress the desiccant, there is a compression spring between the inner and the outer housing. The compression spring ensures that the desiccant remains compact, even under extreme vibrations and shocks, and effectively prevents the individual particles or pearls of the desiccant from rubbing against each other, thus causing abrasion. 
     A disadvantage of the prior art is that it is not possible to completely fill the outer housing with desiccant. Usually, the inner housing is first filled with desiccant, closed, and then inserted into the outer housing. Since the filling must take place from the curved side, the desiccant can only be filled up to the outer edge of the inner housing. 
     U.S. Pat. No. 6,484,413 discloses an air dehumidifier having an inner housing which adjusts to the curved contour of the outer lid, but compression springs are provided on the opposite side to support an axially movable lid. A disadvantage of this known device is that a cavity that cannot be filled is created, which might provide a bypass path for the air that is to be dehumidified. 
     SUMMARY OF THE INVENTION 
     The present invention is intended to avoid the mentioned disadvantages and to provide a desiccant box for dehumidifying air that has an optimum filling level and enables process-reliable filling. 
     The main advantage of the invention is that there are two inner housings or two chambers in the desiccant box which optimally adjust to the outer contour of the overall system. Both inner housings/chambers are completely filled with desiccant and connected to each other during assembly. The two inner housings are arranged concentrically to each other and fill the cylindrical outer housing almost completely. 
     In one embodiment of the invention, at least one of the two inner housings shall be equipped with an air-permeable lid. That facilitates assembly, i.e. it prevents the granulated desiccant from flowing out of the housing when the two inner housings are put together. 
     In a further embodiment of the invention, both inner housings are equipped with air inlets/outlets. They are arranged such that the air to be dehumidified flows through the granules as evenly as possible. To facilitate assembly, both inner housings are equipped with snap-in connections at their coupling point; in particular, such a connection can be realized economically and easily, especially with plastic housings. Instead of snap-in connections, it is also possible to give one of the two parts a conical design in order to connect them. A compression spring acts centrally on both inner housings which form a structural unit, and its pressure is transmitted to the desiccant, so it is not shaken up, even when the device is used for a long time. 
     To avoid the ingress of dust or filth via the air that is to be dehumidified, a filter element in the form of a particle filter can be provided inside the outer housing. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional representation of a desiccant box, consistent with the present invention; 
         FIG. 2  is a sectional representation of one variant of a desiccant box, consistent with the present invention; 
         FIG. 3  is a sectional representation of another variant of a desiccant box, consistent with the present invention; and 
         FIG. 4  is a sectional representation of another variant of a desiccant box, consistent with the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The discussion is now directed to  FIGS. 1 ,  2 ,  3  and  4 . The desiccant box according to  FIG. 1  consists of an outer housing  10  that is closed by a lid  11 . The lid  11  and the outer housing are connected by means of a flanged plate  26 . The flanged plate  26  has a sealing element  27 . The lid  11  features one or more inflow openings  14  and a thread  28  in the flange plate  26  surrounding an outflow opening  15 . The thread  28  adapts the desiccant box to be connected by a hollow pipe segment to a carrier plate  29 , which is illustrated only in outline. 
     Within the cylindrical outer housing  10 , there is a cylindrical first inner housing  12  that abuts the lid  11  through an inserted seal  30 . This inner housing  12  is filled with desiccant granules  13  up to the upper edge  31 . Above the first inner housing  12 , there is second inner housing  17  that is also filled with desiccant  18 . This second inner housing  17  is closed by means of a lid  19 . 
     Once the second inner housing  17  has been filled with desiccant  18 , the lid  19  prevents the desiccant  18  from falling out during handling or when the second inner housing  17  is connected to the inner housing  12 . 
     The second inner housing  17  has air inlets  20 , and the inner housing  12  has air outlets  21 . The air to be dehumidified flows through the lid  11  via the inflow openings  14 , it then flows through a filter element  24  designed as an air-oil separator element, and it reaches the desiccant bed via the air inlets  20 . The second inner housing  17  is in contact with a compression spring  23  that is supported by the contour  16  of the outer housing  10 . The compression spring  23  functions to immobilize the desiccant, so the filling cannot loosen. 
     Inside the compression spring  23 , at the support surface for the compression spring, there are also air inlets  25  which ensure that the air also flows through the desiccant in the center. 
     To facilitate assembly, the first inner housing  12  and the second inner housing  17  are equipped with snap-in connections  22  at their coupling point; in particular, such a connection can be realized economically and easily, especially with plastic housings. A compression spring  23  acts centrally on both inner housings  17 , 12  which form a structural unit, and its pressure is transmitted to the compression medium, for example desiccant  13 , 18 . The snap-in connection  22  is operable to slidably connect the inner housings  12 ,  17  such that the desiccant can be compressed by the compression spring  23 . Action of the compression spring  23  operates to maintain compression on the desiccant  13 , 18  with the effect that the desiccant  13 , 18  remains immobilized even when the device is used for a long time. 
     The variant of the present invention according to  FIG. 2  shows a desiccant box with a reversed inner housing  50 . In the reversed inner housing  50  of  FIG. 2 , the concentric snap-in connection  51  between the lid  32  and the inner housing  50  is positioned proximate to the outlet opening  15  side of the desiccant box. The concentrically designed snap-in connection  51  is operable to slidably connect the inner housing  50  and the lid  32  such that the desiccant  13  can be compressed by the compression spring  54 . In all provided drawing Figures, identical components are shown with the same reference numbers. The contour of the lower part of this inner housing  50  is curved. At the lower part of the inner housing  50  a compression spring  54  is clamped between the inner housing  50  and the contour  16  of the outer housing  10 . The inner housing  50  is closed with a lid  32 . The lid  32  is sized and configured to snap into the inner housing  50 , for example, and be supported by the lid  11  of the desiccant box. The inner housing  50  includes air inlets  52  in a portion of the inner housing  50  proximate to the contour  16  and air outlets  21  in a portion of the inner housing  50  proximate to the outflow opening  15 . 
       FIG. 3  shows another variant of the present invention that features an housing  56  that defines a first inner housing having a first chamber  58  and a second inner housing having a second chamber  57 . The chambers  57 ,  58  are configured to receive desiccant  13  and are arranged concentrically to each other. The chambers  57 ,  58  are separated from each other by a cylindrical wall  33 . Advantageously, the cylindrical wall  33  permits the air to be dehumidified to flow to through the desiccant  13  for a longer time due to the extend flow through path. The air flows into the outer chamber  57  as shown by arrow  34 ,  35 , then through an area of the upper contour as shown by  36 ,  37 . Air then flows into the inner chamber  58  as shown by arrows  36 ,  37 , and leaves this inner chamber  58  as shown by arrow  38  in downward direction through the threaded outflow opening  39 . A lid  66  is slidably connected to the outer housing  10  and the cylindrical wall  33 , the slidable connection operable to permit the compression spring  68  to compress the desiccant in the chambers  57 ,  58 . 
       FIG. 4  shows another variant of the present invention that extends the through-flow time as well. For this purpose, a cylindrical wall  40  is provided in the desiccant  13 , defining an inner chamber  62  and an outer chamber  60 . The chamber  62  defines a first inner housing and chamber  60  defines a second inner housing. A lid  68  is slidably connected to the cylindrical wall  40  separating chambers  60 , 62 , the slidable connection being operable to permit compression of the desiccant  13  by action of the compression spring  42 . In a similar fashion to the discussion of  FIG. 3 , air flows through outer chamber  60  and inner chamber  62  and leaves the drying system (desiccant box) via the threaded outflow opening  64 , dehumidified and purified. 
     The purification takes place by means of a fleece  41  (which serves to remove larger particulate contaminants) together with the compression action of the spring  42  that operates to maintain the desiccant bed  13  tightly packed providing a tortuous paths to air flow and advantageously increasing the efficiency of water removal from the filtered air stream. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.