Abstract:
An improved filter drier for a refrigeration system having a replaceable tubular filter element is shown. A desiccant assembly is removably secured within a housing. The assembly includes a first and second molded desiccant, a hollow tubular perforated core located within said first and second molded desiccant, and a tubular filter located over said core.

Description:
RELATED APPLICATIONS 
     This application is claiming the benefit, under 35 USC §119(e), of the provisional applications filed Nov. 10, 1999 and Mar. 28, 2000, under 35 USC §111(b), which were granted the Ser. Nos. of 60/164,789 and 60/193,166. The provisional applications, Ser. Nos. 60/164,789 and 60/193,166, are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to the refrigeration industry. More particularly, the present invention relates to an apparatus used for the removal of solid particles and water from refrigerant fluids and gases. Most particularly, the present invention relates to an improved filter-drier having a replaceable tubular-type filter element, and a simplified construction. 
     2. Discussion of the Related Art 
     It is widely recognized in the refrigeration field that contaminants are present in the various fluid and gas circuits of refrigeration systems. These contaminants can include moisture, dirt, acids, sludge and varnish, and are generated from various sources including initial manufacturing debris, corrosion, compressor wear, desiccant granules, and overheating conditions. 
     Most commonly, acids, sludge and varnish are produced during unusual elevated, high temperature, or overheating situations. Thus, moisture and dirt are of the most concern under normal operating conditions, and most filter driers in the art are directed to removing water and solid particulates. 
     Water or moisture is always present in refrigeration systems. Acceptable limits vary from one unit to another, and from one refrigerant to another. Moisture is harmful even if “freeze ups” do not occur. And therefore it is desirable to keep the moisture level as low as possible. 
     Solid particulates such as dirt, oxides, scale, sludges, flux and metallic particles are frequently found in refrigeration systems. Numerous metallic contaminants such as cast iron dust, rust, scale, steel, copper and brass chips can damage cylinder walls, bearings, and plug capillary tubes or thermostatic expansion valve screens. In addition to mechanical damage and “plug ups”, these contaminants catalyze chemical reactions that contribute to decomposition of the refrigerant-oil mixtures at elevated temperatures, and thus, it is also desirable to remove as much dirt as possible from refrigeration systems. 
     As a result, efforts have been made in the art to remove water and solid particulate contaminants using various devices. However, there are limitations to the effectiveness of these current filtration techniques. 
     Fiber glass pads and wire mesh screens have typically been used to remove solid particulants in refrigerant. Due to their construction, they have very little propensity to remove water. These pads and screens have been typically flat, and circular in shape, and located at the outlet of a housing. While this shape has advantage for fabrication costs, the effectiveness of the filtration performance has been limited. The filtration surface area of the circular shape is equal to or less than the cross-sectional area of the housing. 
     The results of this relatively small filtration surface can evolve in two ways. First, if the filter pads are designed to retain very small particles, which is desired for the protection of the system, the flow restriction through the pads will be very high, and the life will also be very short because of the fast contamination build-up. 
     Alternatively, if the filter pads are designed to have low flow restriction, the retention of the desired small particles will not occur, and the protection of the system will be compromised. 
     Desiccants have been used for many years to remove water and are generally constructed in two forms. Firstly, desiccant beads (approximately 0.10″ in diameter) have been put into various forms (flat beds, hollow cylinders, etc.) by using materials, such as wire mesh, or perforated steel sheet, to create the desired configuration. This construction, while giving large surface areas for water removal, has very limited filtration capacity due to the large flow path channels through the bead matrix. Also, due to the loose form of the bead bed, the beads can rub against the retaining structure, as well as each other. This rubbing action can dislodge particles from the beads, and become a contaminant within the refrigeration system. 
     Alternatively, desiccants have also been rigidly molded into various shapes by using a combination of binders, temperature, and pressure, and are typically referred to as a desiccant core. The desiccant cores offer improved filtration characteristics due to the use of smaller desiccant granules, and their rigid form. The combination of small desiccant granules being held together creates a matrix which provides solid particulate retention capability. However, the solid particulate can be dislodged from the molded core and become a contaminant. This particulate can be generated from abrasion with other components during assembly, shipping damage, and residue from the desiccant core molding manufacturing process. 
     While such a filter-drier is generally satisfactory in operation, it still suffers from the aforementioned problems of limited filter area. In addition, replacing the desiccant cores is a fairly complicated operation. Thus, those skilled in the art continued to search for an improved filter-drier with a simplified structure, and increased filtration effectiveness. 
     SUMMARY OF THE INVENTION 
     The present invention solves the long standing problems in the art by providing a filter-drier with a core-type construction in place of the previously used coreless construction. A hollow support core is sealingly attached at one end thereof about an aperture in an end cap, thus providing communication with the interior of the hollow support core. The other end of the hollow support core is sealingly closed by a closure member having an aperture or protuberance to permit fastening an opposing end cap to the other end of the hollow support core. A tubular filter is placed over the hollow support core. One or more of the known molded desiccant cores are placed over the tubular filter and held in place between the end caps. Thus, filtration area is greatly increased, and a simplified construction is provided. 
     Thus, one of the objects of the present invention is to overcome the shortcomings of conventional filter-driers. 
     Another object of the present invention is to provide an improved filter-drier having a greatly increased filtration area. 
     A further object of the present invention is to provide a simplified construction for a filter-drier. 
     A still further object of the present invention is to provide a filter-drier which is more economical to manufacture. 
     A further object of the present invention is to provide a filter-drier having a tubular filter in place of the circular screen filter known in the prior art. 
     Further objects and advantages of the present invention will be apparent from the following description and appended claims, reference being made to the accompanying drawings forming a part of the specification, wherein like reference characters designate corresponding parts in the several views. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a known filter drier of the type having a circular flat screen filtration element. 
     FIG. 2 is a sectional elevational view of a construction embodying the present invention. 
     FIG. 3 is a sectional view, taken in the direction of the arrows, along the section line  3 — 3  of FIG.  2 . 
     FIG. 4 is a sectional elevational view showing a modification of the construction shown in FIG.  2 . 
     FIG. 5 is a fragmentary view of the upper portion of the construction shown in FIG. 4, on an enlarged scale. 
     FIG. 6 is a fragmentary elevational view, on an enlarged scale, of the lower portion of the construction shown in FIG. 4, on an enlarged scale. 
     FIG. 7 is a sectional elevational view of a further modification of the present invention. 
     FIG. 8 is a fragmentary view of the lower portion of the construction shown in FIG. 7, on an enlarged scale. 
     FIG. 9 is an exploded, perspective view of the tubular filter shown in FIGS. 7 and 8. 
     FIG. 10 is a sectional view, taken in the direction of the arrows, along the section line  10 — 10  of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to the present invention, there is shown an apparatus to provide improved filtration effectiveness in refrigeration systems. The apparatus can be configured to fit within existing housing designs, and also provides for improved assembly and disassembly of the components within the housing. 
     A refrigeration circuit is generally a closed loop system. Tubing connects the various components of the system (compressor, expansion valve, heat exchanger, etc.) which is not open to the environment, except during service. For ease of understanding the present invention and improvements which are present therein, a prior art filter-drier is first described. 
     Referring to FIG. 1, the filter-drier  20  comprises a housing  21  having an inlet  22 , and an outlet  23 . A flange  24  is provided on the housing  21  proximate the bottom thereof. Flange  24  has a plurality of apertures  25 . To seal the open end of housing  21 , a housing cover  26  is sealingly attached to the lower annular surface  27  of the housing  21 . This is accomplished by providing an equal plurality of axially alignable cover apertures  28  which will align with apertures  25  when the housing cover is in place. A gasket  29  is provided in gasket groove  30  and a spring groove  31  is provided for purposes to be described below. When housing cover  26  is secured to housing  21  with bolts  51 , and nuts  52 , the interior of the filter-drier  20  will be sealed, and communicate with the circuit only through inlet  22  and outlet  23 . 
     The interior of housing  20  will accept a desiccant assembly  32 . The desiccant assembly  32  comprises seriatim a first end cap or core end plate  35 , a first molded desiccant core  36 , a core separator  37 , a second molded desiccant core  38 , flat mesh screen  42 , and a second end cap or core base plate  39 . 
     A plurality of radially extending retainers  40  are provided on core end plate  35 , core separator  37 , and core base plate  39 . Slots  46  are provided in retainers  40 . 
     A plurality of retaining screws  43  having head portions  44  and threaded portions  45  are provided. To assemble the desiccant assembly  32 , the parts are assembled seriatim as previously described. 
     Slots  46  will be placed in axial alignment before assembly begins. Head portions  44  of the retaining screws  43  will be placed into slots  46  in retainers  40  of the core base plate  39 , and the shafts of the retaining screws  43  will be laid into the slots  46  of the retainers  40  of the core separator  37  and the core end plate  35 . This will position the threaded portions  45  of the retaining screws  43  below the retainers  40  in the core end plate  35 . 
     A second gasket  41  is installed in the gasket groove  41 A provided in the core base plate  39 . A spring  50  is then interposed between the core end plate  35  and the spring groove  31  in the housing cover  26 . The desiccant assembly is then attached to housing cover  26  by threading the threaded portions  45  of retaining screws  43  into threaded apertives  45 A in housing cover  26 . This assembly is inserted into housing  21 , and housing cover  26  is attached to housing  21  using bolts  51  and nuts  52 , thus sealingly installing desiccant assembly  32  in housing  21 . 
     In operation, gas or fluids will flow into the inlet port  22  through the first molded desiccant  36 , the second molded desiccant  38 , screen  42 , through openings  47 , and out the outlet port  23 . It should be understood that the details of construction of the prior art desiccant filter may vary somewhat from the illustration. It is common practice to use from one to four molded desiccants depending on the application, which may eliminate the need for the core separator  37 , or require up to three core separators  37 . 
     It can be seen in this construction that the area of the wire mesh screen  42  is limited, and may be less than the diameter of the housing  21 . In the prior art construction there is no way to overcome this problem. 
     Referring now to FIGS. 2 and 3, a construction embodying the present invention is shown whereby the filter area is greatly increased over the prior art devices, as is the ease of assembly of the desiccant assembly. 
     The construction of the filter-drier  20  may be identical to that previously described, and will not be repeated herein. The desiccant assembly, now indicated by the numeral  60  for the purposes of clarity, is no longer coreless, as was the desiccant assembly  32  of the prior art. Instead, a perforated core assembly  61  is provided to hold the first molded desiccant  36  and the second molded desiccant  38 . The perforated core assembly  61  comprises a tubular perforated core  62  having a plurality of perforations  62 A, which may be of seamless, seamed, or other construction, as desired. The tubular perforated core  61  is closed at a first end by a first closure member  63 . The first closure member  63  has a threaded portion or protuberance  64  for attachment to a first end cap or core end plate  72  in a manner to be described hereinafter. 
     The surface of the first closure member  63  opposite the threaded portion or protuberance  64  has a parametric or annular recess  65  which accepts the first end  66  of the hollow tubular perforated core  62 . The perforated core  62  is fixedly attached to the first closure member  63  by the use of welding or other attachment means well known in the art. Below annular recess  65  is an annular or parametric channel  70  which accepts seal or O-ring  71  for purposes to be described. 
     First end cap or core end plate  72  having a mating weld nut  73  affixed thereto by means known in the art will screw onto the threaded portion or protuberance  64  of the first closure member  63 . 
     At its other end, tubular perforated core  62  is attached to a second end cap or core base plate  75 . Second end cap  75  comprises a first portion  77  attached to a second portion  78 . 
     First portion  77  comprises a first annular portion  77 A having a gasket recess  82  formed about the outer perimeter thereof and a downwardly depending sidewall  84  having an inside diameter substantially the same as the outside diameter of the second molded desiccant  38 . At the inner extremity of the first portion  77 A is a downwardly depending stepped wall  77 C having a first step  77 D and a second step  77 E. The outside diameter of the stepped circular wall  77 E will be essentially the same diameter as the second annular portion  78  of second end cap  75 . 
     Second portion  78  has a radially outwardly extending flange  78 A and a downwardly depending sidewall  78 B. When assembled to first portion  77  of second end cap  75  an outwardly facing annular channel  79  will be formed to accept seal or O-ring  80 , and the downwardly depending sidewall  78 B will accept the other end of tubular perforated core  62 , which will be affixed thereto by welding or other suitable means known in the art. A filter tube  88  having top U-shaped retainer  89  and lower U-shaped retainer  90  will fit over the hollow tubular perforated core  62  and seal against first O-ring  71  and second O-ring  79 . 
     To assemble the perforated core assembly  61 , the second end cap  75 , having tubular perforated core  62  attached, may be placed on a flat surface, held in a jig or a fixture, or otherwise restrained. The filter tube  88  is slipped over the vertically oriented perforated core  62  until O-rings  80 , 71  seal against U-shaped retainers  89 , 90 . Second desiccant core  38  is then placed over the tubular filter  88  until it comes to rest against second end cap  75 . Core separator  102  is then placed over the exposed end of the second molded desiccant  38 , and first molded desiccant  36  is placed over the tubular filter  88  until it meets the core separator  102 . First end cap  72  is then screwed onto threaded portion  64  of the first closure member  63 . The gasket  81  will then be inserted in the gasket groove  82 . Generally the inside diameter of the gasket  81  will be a press fit into the gasket groove  82  so the gasket will remain in place. 
     Essentially the desiccant assembly  60  has been assembled upside down with respect to its position in use, as the desiccant assembly will now be inserted into the housing  21  until the gasket  81  seals against the upper portion of the housing  21 . The spring  50  will be placed over the boss  72 A on first end cap  72 , and then the other end of spring  51  will be placed in spring groove  31  of the housing cover  26 . A plurality of bolts  51  will be passed through apertures  25  in the housing cover and the radially extending flange  24  of the housing  21 , nuts  52  will be applied to bolts  51  and the bolts  51  will be tightened applying pressure to the desiccant assembly  60  to force the gasket  81  into sealing engagement between the housing  21  and the second end cap  75 . The entire filter-drier  20  will then be turned over and installed for use in the position shown in FIG.  2 . It should be understood that the position shown is for illustrative purposes only, and the filter-drier  20  can be used in any desired position. 
     Air entering inlet  22  will pass through the molded desiccants  36 , 38  through the filter tube  88 , through the perforations  62 A in the hollow perforated tubular core  62 , and out through the outlet  23 . Solids, particulates, and water will be removed from refrigerant systems in an efficient and economical manner. 
     Referring to FIG. 3 it can be seen that the first end cap  72  the core separator  102  and the second end cap  75  may have retainers  40  provided in a spaced apart peripheral orientation, as in the prior art filter-drier just described. While these retainers are no longer used to hold the desiccant assembly  60  together, they do provide spacing for the assembly  60  within the housing  21 . 
     It should be understood that more than one desiccant assembly  32  may be used, and each desiccant assembly may contain less than 2 or more than 2 desiccant cores  36 . Also, the filtered drier  20  may be used without any desiccant assembly  32  or desiccant cores  36 , and serve as a filter. 
     Referring now to FIGS. 4-6, there is shown a modification of the present invention. Essentially the construction of the modification shown in FIGS. 4-6 is identical to the construction shown in FIGS. 2-3, except for a few features. The retainers  40  previously provided on second end cap  72  or core base plate are removed and replaced by a radially extending flange  106  entirely about the periphery of the second end cap  72 . The core separator  102 , instead of having an upstanding perimetral wall  103  and retainers  40  thereon, has an outer down standing perimetral wall  108  and an upstanding inner perimetral wall  110  to aid in the location of the first molded desiccant  36  and the second molded desiccant  38 . The inside diameter of the outer downstanding perimetral wall will be chosen to be approximately the same as the outer diameter of the first molded desiccant  36 . The outside diameter of the inner upstanding perimetral wall will be approximately equal to the inside diameter of the second molded desiccant  38 , while the inside diameter of the inner upstanding perimetral wall  110  will be approximately the same as the outer diameter of the filter tube  88 . As before the filter tube  88  will be in sealing engagement with the first O-ring  71  and the second O-ring  80 . 
     The second end cap or core base plate  75 , instead of having the downwardly depending perimetral sidewall  84  and retainers  40  thereon has a downwardly depending, outwardly slanting, perimetral sidewall  112 . The core separator still performs its function of aiding and locating of the first and second molded desiccants  38  but no longer provides the function of assisting location of the desiccant assembly  32  within the housing  21 . Instead the radially extending flange  106  on the first end cap  72 , and the outwardly slanted, downwardly depending, sidewall  112  on the second end cap  75  perform this function. 
     Referring now to FIGS. 7-9 a further modification of the present invention is provided which provides the same advantages, but which is easier and more economical to manufacture. A stronger filter tube (FIG. 9) is provided by replacing the U-shaped retainers  89 , 90  with two piece retainers  115 , each comprising an annular portion  116  and an annular L-shaped portion  117  of slightly differing diameters. The filter tube is placed over the L-shaped portion and the annular portion is then placed over the filter tube (or vice versa). Since the L-shaped portion and annular shaped portion of the retaining ring are of slightly differing diameters, the filter material will be pinched between the L-shaped ring and annular ring, and will be sealingly engaged by the retainers  115 . A supporting member  118  may be interposed between the annular ring portions  116  of retainers  115  and the filter material, and it will also be held in place by friction and add support to the tube. 
     It should be understood that the filter tube  88  may be of any construction known in the art. In the embodiment illustrated in FIG. 9, a single mat or layer of filter material or filtering medium  88 A is formed into a tubular shape and inserted in the retainers  115 . More than one layer of filter material or filtering medium may be used if desired. Also, the supporting member  118 , if desired, may be crimped over one end of the filter material. This will help seal the ends of the mat  88 A. A formed filter tube may also be used if desired. Referring to FIGS. 7 and 8, other differences in construction over those illustrated in FIGS. 4-6 may be seen. 
     In the modification of the invention shown in FIGS. 7-8, the construction of the desiccant assembly, now identified by the numeral  125 , is modified for ease and economy of construction. The hollow tubular perforated core assembly  126  has a modified first closure member  127 . The modified first closure member  127  consists of a circular end piece  128  having a central threaded opening  129 , to receive a bolt or other fastening means  130 . The first closure member  127  is essentially circular in shape and has an outwardly facing perimetral channel  131  (FIG. 8) containing a second O-ring  132 , and a perimetral groove  133  to receive one end of the tubular core  135 . The second closure member  138  is generally annular in shape and has a first groove  140  which accepts the upper end of tubular core  135 , in this case made of expanded metal mesh, and enables the tubular core  135  to be securely welded or otherwise attached to second closure member  138 . Second closure member  138  also has a second groove  143  which fits in a central opening  144  provided in a modified second end cap or core base plate  145 . 
     Modified second end cap  145  has, in addition to the central opening  144 , a seal groove  148  in which a seal  149  is carried, a downwardly depending sidewall  150  and a radially extending flange  151  which is annular in shape and extends from the distal end of the downwardly depending sidewall  150 . The diameter of the radial flange  151  is just slightly smaller than the inside diameter of the housing  21  to help locate the modified desiccant core assembly  125  in the housing  21 . 
     The remainder of the construction of the desiccant assembly  125  of this modification remains essentially the same as that previously described. The assembly of the desiccant assembly  125  to insert into the filter-drier housing  21  would be essentially the same except for the step of screwing on the first modified end cap  153 . In this case the end cap  153  would simply be placed over the end of the first molded desiccant  136 , a bolt  130  would be inserted through the opening  155  in boss  156  of the first end cap  153  and engage the threaded opening  129 . A head seal  157  would be provided between the bolt  130  and the end cap  153  to prevent leakage at the point of attachment. The end cap  153  would seal by means of a further gasket  158  between the end cap  153  and first molded desiccant  36  as before. 
     Therefore, by carefully considering the problems present in the filter-drier industry, I have developed a novel and unique perforated core assembly for a filter drier. 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.