Patent Abstract:
A desiccant container for use in an accumulator or a receiver/dryer of a vehicle includes at least one integral mesh screen for preventing small particles from passing therethrough. Preferably, the container includes two integral mesh screens, one forming an upper surface of the desiccant container and the other forming a lower surface of the desiccant container. By incorporating integral mesh screens, the container need not include separate filters.

Full Description:
FIELD OF THE INVENTION 
   The invention relates to containers for desiccants and is particularly concerned with desiccant containers used within heating, ventilation and air conditioning (HVAC) systems. 
   BACKGROUND OF THE INVENTION 
   The invention relates to desiccant containers for any purpose. However, specific embodiments will be described with respect to desiccant containers within HVAC systems. 
   A typical vehicle air conditioning system, for example, incorporates a compressor, a condenser, an expansion device, an evaporator and a refrigerant storage device. The compressor compresses refrigerant. The refrigerant flows to the condenser, where it changes state from gas to liquid. In a system with a thermal expansion valve (a “TXV system”), refrigerant then passes into a refrigerant storage device called a receiver/dryer (R/D) before passing to the expansion device. In a system with a fixed orifice tube (an “FOT system”), refrigerant then passes directly from the condenser to the expansion device. The expansion device is used to significantly lower the pressure and temperature of the refrigerant before it passes to the evaporator. After the expansion device, the liquid refrigerant then flows to the evaporator. At that stage, an air blower passes air over the evaporator to the passenger compartment of the vehicle, thereby cooling the air within the vehicle. The heat transfer from the ambient air to the evaporator causes most of the refrigerant to change from a liquid to a gas. 
   In an FOT system, the refrigerant (now mostly gas and some liquid) flows from the evaporator to a refrigerant storage device called an accumulator. (In a TXV system, the refrigerant flows from the evaporator to the compressor directly.) 
   One purpose of the accumulator is to separate liquid refrigerant from gaseous refrigerant, so that only gaseous refrigerant returns to the compressor. Liquid refrigerant entering the compressor causes “flooding” which in turn reduces system efficiency and can damage the compressor. Hence it is standard practice to include an accumulator between the evaporator and the compressor to separate and store the excess or residual liquid. The residual liquid refrigerant in the accumulator eventually turns to a gaseous state and is then passed to the compressor. 
   Accumulators and receivers/dryers often incorporate a desiccant to prevent (or at least limit) moisture ingression in the compressor and the resulting damage or loss of efficiency to the air conditioning system. (For simplicity, hereinafter, the term “accumulator” or “refrigerant storage device” will refer to both accumulators and receiver/dryers.) 
   Particulate desiccants are often used in such systems because of the high area-to-volume ratios of the particles with respect to the surrounding air or fluid. Because the desiccant particles must be held in the air or fluid stream and prevented from contaminating other parts of the air conditioning system, the particles must be held in a container which is permeable to the air or fluid but impermeable to the particles. 
   In some known cases, loose desiccant is contained within a bag, the bag being constrained between filters. The filters are often discs made of felt, gauze, fiber or plastic (fused). Such bags are problematic because they can be easily damaged during assembly and/or testing. A tear in the bag allows the loose desiccant particles to escape and potentially enter the air-conditioning system, where they can damage the accumulator and other components. 
   In certain other systems, it is known to confine the desiccant within a hard container. In those cases, filter discs, such as those described above, are typically placed in the top and bottom of the desiccant container during manufacturing. However, there are certain drawbacks associated with the use of such filter discs. For example, the materials used within the filter discs, such as polyester or polypropylene matted or needles felt, for example, have been known to stimulate a reaction with the air conditioning refrigerant R-134A to create a significant noise within the air conditioning system. It would be desirable to eliminate the noise. It would also be desirable to eliminate the cost associated with the purchase of the filter discs. It would also be desirable to eliminate the time and cost associated with their installation within the desiccant cup. It would also be desirable to eliminate filter discs because they deteriorate during service and release high aspect ratio fibres into the air conditioning system. 
   A number of desiccant cups are known which have a one-piece cup with a one-piece cap, such as that taught in U.S. Pat. No. 5,522,204 in the name of Wood. The cup taught in Wood incorporates holes formed within the cap and cup bottom. However, such cups require additional filter layers placed against the cap and cup bottom. As well, holes formed within the cap and cup bottom in this manner have a number of drawbacks. One drawback is that diameter of the holes is large enough to allow desiccant particles to pass through or become caught or blocked in the holes. Therefore, such cups require a separate filter. As well, it would be desirable to have a more open area for fluid to pass through than is permitted through an array of holes, such as taught in Wood, because more open area reduces pressure drop in the system, thereby increasing efficiency. 
   SUMMARY OF THE INVENTION 
   According to a first aspect, the invention provides a desiccant container for use in a refrigerant storage device of a vehicle, the container comprising a lid comprising an inner boundary defining a first aperture, an outer boundary surrounding the inner boundary, and an integral first mesh screen extending between the inner boundary and the outer boundary, wherein the first mesh screen is adapted to prevent small particles from passing therethrough; a body comprising an inner wall defining a second aperture, an outer wall surrounding the inner wall, and an integral second mesh screen extending between the inner wall and the outer wall, wherein the second mesh screen is adapted to prevent small particles from passing therethrough; wherein the lid and the body are adapted to fit together to create an enclosed cavity, and to prevent small particles from passing between an edge of the lid and the body, and when the lid and the body are together, the first aperture and the second aperture are aligned. 
   According to another aspect, the invention provides a desiccant container for use in a refrigerant storage device of a vehicle, the container comprising at least one integral mesh screen, each mesh screen preventing small particles from passing therethrough. 
   According to yet another aspect, the invention provides a refrigerant storage device for a vehicle, the refrigerant storage device comprising a desiccant container wherein the container comprises at least one integral mesh screen, each mesh screen preventing small particles from passing therethrough. 
   Advantageously, different embodiments of the present invention may permit: the elimination of noise created in the air conditioning system when polyester, polypropylene matted, other matted synthetic fibre, cotton fibre, low permeation or needled felt are used as filters; the reduction of cost by eliminating the need to purchase separate filters for the desiccant container; the reduction of time and cost relating to the labour required to install separate filters for the desiccant container; a desiccant container incorporating integral filtration with significant open area, thereby reducing pressure drop (as compared to a container with less open area); the provision of a filter for 100% of the liquid above the oil bleed hole of the accumulator, which provides a significant advantage since a typical oil bleed filter (located in or near the oil bleed aperture) is small in size and can become partially or completely blocked with a relatively small amount of contamination (thereby disrupting oil flow); and increasing the efficiency of the air conditioning system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention will now be described with reference to the attached drawings in which 
       FIG. 1  is a side view of a representative accumulator, with certain features inside the accumulator, including a desiccant container, shown by dotted outline in accordance with an aspect of the present invention; 
       FIG. 2   a  is a perspective view of a desiccant container in accordance with an aspect of the present invention; 
       FIG. 2   b  is a perspective view of a lid of the desiccant container of  FIG. 2   a;    
       FIG. 2   c  is a side view of the lid of  FIG. 2   b;    
       FIG. 2   d  is a perspective view looking down on the body of the desiccant container of  FIG. 2   a;    
       FIG. 2   e  is a perspective view looking up at the body of the desiccant container of  FIG. 2   d;    
       FIG. 2   f  is a perspective view of an alternate embodiment of a desiccant container; 
       FIG. 2   g  is a perspective view of a desiccant cup of the desiccant container of  FIG. 2   f;    
       FIG. 2   h  is a perspective view of the desiccant cup of  FIG. 2   g , looking up; 
       FIG. 3   a  is a partial cut-away, side view of a portion of the accumulator of  FIG. 1 ; and 
       FIG. 3   b  is cross-sectional view of the desiccant container of  FIG. 2   f  within the accumulator of  FIG. 1 , taken along line  3   b – 3   b  of  FIG. 1  (with the outlet tube omitted). 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a representative accumulator or refrigerant storage device  10  for an air conditioning (or heating, ventilation and air conditioning (HVAC)) system of a vehicle. The accumulator  10  as shown in  FIG. 1  has certain features omitted for simplicity and certain features inside the accumulator  10  are shown by dotted outline. A desiccant container  12  according to an aspect of the present invention is shown roughly in position within the accumulator  12 , for example purposes. 
     FIG. 2   a  is a perspective view of the desiccant container  12 . The desiccant container  12  has two portions, namely an open body or cup portion  14  and a lid  16 .  FIG. 2   b  is a perspective view of the lid  16 .  FIG. 2   d  is a perspective view of the open cup  14 . 
   As perhaps best seen in  FIG. 2   b , the lid  16  is a one-piece casting. The lid  16  is a generally circular, one-piece casting, having a generally circular outer or peripheral boundary  20  and a concentric, generally circular, inner boundary  22 , forming an opening  24  therein. Between the peripheral boundary  20  and the inner boundary  22  is an integrally molded mesh screen  30 , advantageously supported and strengthened by an integrally molded, lattice support structure  32 . Preferably, the mesh screen  30  has a low profile. As shown in  FIG. 2   b , the profile of the inner boundary  22  and the profile of the peripheral boundary  20  may be higher than the profile of the mesh screen  30 . Similarly, the profile of the support structure  32  may be higher than the profile of the mesh screen  30 . 
   As shown in  FIGS. 2   b  and  2   c , an outer surface  34  of the peripheral boundary  20  advantageously has an integral bead  36  or series of beads extending outwardly therefrom. 
   As perhaps best seen in  FIG. 2   d , the cup  14  is a one-piece casting. The cup  14  incorporates a generally cylindrical inner wall  40 , and a concentric, generally cylindrical outer wall  42 . The inner wall  40  and the outer wall  42  are joined by an integrally molded bottom portion  44  extending between the inner wall  40  and the outer wall  42  and connecting with the inner and outer walls  40 ,  42  at or near their bases. The bottom portion  44  comprises a mesh screen  46  supported and strengthened by an integrally molded, lattice support structure or grid  50 . Advantageously, the mesh screen  46  has a low profile. As shown in  FIG. 2   d , the profile of the support structure  50  may be higher than the profile of the mesh screen  46 . The support structure  50  also acts as a gating system for the injection molding process. 
   The support structure  50  for the mesh screen  46  of the cup  14  may be deeper and/or wider than the support structure  32  of the mesh screen  30  of the lid  16 . The support structure  32  in the lid  16  may be less deep and less wide to reduce the weight of the lid and to reduce the height of the lid. The precise geometry, configuration, and size of the support structures  32  and  50  may be varied. Although the support structures  32  and  50  could be omitted, they do provide certain advantages. Among other advantages, the support structures  32  and  50  help maintain a resistance to distortion during the molding process and they provide support for the finished product. 
   The bottom portion  44  of the cup  14  and the lid  16  each have an open area of approximately 30%. However, this percentage could vary depending upon many factors, including the size of the mesh screen openings  30  and  46 , as well as the strength and configuration of the support structures  32  and  50 , for example. The openings within the mesh screens  30  and  46  are sized to restrict the passage of desiccant particles and other particles that may be detrimental to the air conditioning compressor. Ideally, the openings within the mesh screens  30  and  46  are smaller than about 350 microns, and advantageously smaller than about 300 microns. 
   According to one embodiment, the outer surface of the inner wall  40  of the cup  14  has an outwardly extending support rib  52  and the outer wall  42  has a corresponding, inwardly extending support rib  54 . Just above the support rib  54  on the inner surface of the outer wall  42 , is a groove  56 . 
   The inner surface of the inner wall  40  of the cup  14  has an inwardly extending outlet tube stop or support rib  60 . As well, as shown in  FIG. 2   e , the inner surface of the inner wall  40  of the cup  14 , below the outlet tube stop  60 , has an inwardly extending step or liner support rib  71 , for supporting the cup  14  on the liner  70 , as described below. 
   Advantageously, on the outer surface of the outer wall  42  of the cup  14 , just below the top edge of the outer wall  42  is an outwardly extending bead  62 . Alternatively, the bead  62  could instead be a series of beads  62  (not shown). 
   In order to use the desiccant cup within the accumulator  10 , loose desiccant (not shown) is placed in the cup  14 . The lid  16  is then placed within the cup  14 . When the lid  16  is lowered within the cup  14 , the inner boundary  22  of the lid rests against a top surface of the support rib  52  of the inner wall  40 , and the peripheral boundary  20  of the lid  16  rests against a top surface of the support rib  54  of the outer wall  42  of the cup  14 . As well, the bead  36  on the outer surface  34  of the lid  16  snaps within the groove  56  of the outer wall  42  of the cup  14  to secure the lid  16  in place. 
   The lid  16  may be further secured to the cup  14  through a number of techniques known to those skilled in the art. One such technique is ultra-sonic welding. One weld (not shown) attaches the inner surface of the inner boundary  22  of the lid  16  to the outer surface of the inner wall  40  of the cup  14 . Another weld attaches the outer surface  34  of the lid  16  to the inner surface of the inner wall  40  of the cup  14 . 
   When the desiccant cup  14  has been filled with desiccant, such as synthetic zeolite or sol-gel silica, for example, and after the lid  16  has been secured to the cup  14 , the cup may be placed within the accumulator  10 . The particular configuration of the desiccant cup  14  and lid  16  described above may be accommodated by the accumulator  10  of the type shown in  FIG. 3 . As shown in  FIG. 3 , the accumulator  10  has an inner liner  72 , which fits within the accumulator  10 . The liner  72  incorporates a central support (not shown) for the cup  14 , which support terminates in an upwardly extending, open, generally circular terminal portion, forming a hole within the terminal portion. The terminal portion of the liner  72  has a diameter sufficient to support the bottom surface of the liner support rib  71  of the inner wall  40  of the cup  14 . The liner  72  may also incorporate a groove  74  in its inside surface. 
   The desiccant cup  14  is placed on top of the terminal portion of the liner  72 . In that position, the bead  62  on the exterior surface of the outer wall  42  of the cup  14  snaps into the groove  74  on the inside surface of the liner  72 , to help secure the cup  14  in position and to prevent passage of particles between the outer wall  42  of the cup  14  and the inside surface of the liner  72 . 
   When the cup  14  is in position within the liner  70 , an outlet tube  80  is placed inside the inner wall  40  of the cup  14 , the outlet tube being supported by the upper surface of the outlet tube stop  60 . 
   Preferably, the elements of the liner  72 , the cup  14  and the lid  16  are adapted to fit together so that particles larger than 350 microns cannot pass from above the lid  16  to below the cup  14 . 
   The cup  14  and the lid  16  could be manufactured from any number of materials known to those skilled in the art including nylon, polyester, and polypropylene materials suitable for use in environments where refrigerant and oil are present. As suggested above, the cup  14  and the lid  16  may be formed by injection molding. 
   Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practised otherwise than as specifically described herein. 
   Of course, there are many other possible configurations to allow a lid and a cup for a desiccant to fit together. There are also many different configurations to allow a desiccant container to fit within an accumulator or receiver/dryer. One example of a configuration different from those described above is shown in the alternate embodiment of  FIGS. 2   f ,  2   g ,  2   h  and  3   b.    
   In the earlier embodiment shown in  FIG. 2   a , the lid  16  fits within the circumference of the cup  14 . However, as shown in the alternate embodiment of a desiccant container  99  of  FIGS. 2   f  and  3   b , the circumference of a lid  100  rests on top of the circumference of a cup  102 . 
   A cross-sectional view of the desiccant container  99  of this alternate embodiment, in place within a liner  104 , is shown in  FIG. 3   b . The lid  100  has an extension portion  106  extending away from a top portion of the lid  100 . A v-shaped projection portion  108  projects downwardly from the extension portion  106 . To help keep the lid  100  in position on the cup  102 , a groove  112  is located along a top surface of the cup  102 . After the lid  100  is placed on top of the cup  102 , the lid  100  may be ultrasonically welded to the cup  102 . 
   The desiccant container  99  is secured within the liner  104  by sliding the desiccant container  99  past a detent  116 , which detent  116  projects inwardly from the liner  104 . 
   As can also been seen from  FIG. 3   b , lower portions of the cup  102  have downward, v-shaped projections  118 , which fit within corresponding v-shaped grooves  122  located within the liner  104 . 
   As shown in  FIG. 3   b , the liner  104  incorporates a projecting support  124 . When the outlet tube  80  (not shown in  FIG. 3   b ) is in place, the outlet  80  rests on top of the projecting support  124 . 
   This alternate embodiment omits a number of elements present in the earlier embodiments described above. For example, the outlet tube stop  60  (as shown in the earlier embodiment of  FIG. 2   d ) and the liner support rib  71  of the inner wall  40  of the cup  14  (as shown in  FIG. 2   e ) have been omitted. As well, the integral bead  36  on the lid  16  of the earlier embodiment of  FIG. 2   c  has been omitted. The groove  56  of the outer wall  42  of the cup as shown in the earlier embodiment of  FIG. 2   d  has been omitted. The bead  62  around the outer wall  42  of the cup  14  (as shown in  FIG. 2   d ) has been omitted. Similarly, the groove  74  on the inside surface of the liner (as shown in  FIG. 3   a ) has been omitted. 
   As noted above, many other possible embodiments are also within the scope of above teachings. For example, it is possible to design a desiccant container without distinguishable lid and cup portions. 
   As another example, although the embodiments described above relate to a desiccant container  12  having two integral mesh screens  30  and  46 , the desiccant container  12  could contain a single integral mesh screen, either  30  or  46 . Instead of the other integral mesh screen, a technique already known by those skilled in the art could be used to provide filtering (such as using a separate filtering device). 
   Many other modifications and/or variations are also possible. For example, there are many different techniques known to those skilled in the art for fitting parts of containers together and for securing containers within other objects. Therefore, for example, techniques different from those described herein could be used to secure the lid  16  to the cup  14 , to achieve a similar result. Various features of the desiccant container  12  have been described as being generally circular (such as the lid  16 , the inner boundary  22  of the lid  16 , the inner wall  40  of the cup  14 , the outer wall  42  of the cup  14 , etc.). However, different configurations could also be used. For example, in the embodiment of  FIGS. 2   b  and  2   d , the lid  16  has an opening  24  which is centered with respect to the outer boundary  20 . Similarly, the opening within the inner wall  40  of the cup  14  is centered with respect to the outer wall  42 . However, both the opening  24  of the lid  16  and the opening within the inner wall  40  of the cup  14  could be off center. 
   The configuration of the desiccant container  12  has been described herein to be adapted to the particular accumulator  10  and liner  72 , described above. However, the basic features of the desiccant container  12  could be adapted for other types and configurations of accumulators, with or without liners and for other purposes (outside of the context of air conditioning systems for vehicles). In other words, the embodiments described above relate to air conditioning systems in vehicles. However, the desiccant containers described herein could be used in air conditioning systems outside of the context of vehicles, and could be used outside of the context of air conditioning systems entirely.

Technology Classification (CPC): 1