CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/244,396 filed on Oct. 2, 2008, which claims the benefit of U.S. Provisional Application No. 60/976,873, filed on Oct. 2, 2007. The entire disclosures of each of the above applications are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to valve plate assemblies, and more specifically to compressor valve plate assemblies. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    Compressor valve plates are typically formed from a series of stamped parts coupled to one another. The valve plates usually include first and second plates with a series of spacers providing support between adjacent surfaces of the first and second plates. The use of stamped parts limits the geometry that the first and second plates may include. This results in the spacers being formed as separate parts, creating additional cost and increased complexity in assembly. 
       SUMMARY 
       [0005]    A compressor valve plate assembly may include a first valve plate formed of a unitary casting that separates a compressor head and a compressor body and defines a suction chamber receiving refrigerant at a suction pressure. 
         [0006]    The first valve plate may define a discharge passage. The first valve plate may include a central recessed portion surrounded by an outer wall integrally formed therewith and extending a height above the central recessed portion. The discharge passage may pass through the central recessed portion. 
         [0007]    The first valve plate may include a central recessed portion defining the suction chamber and surrounded by an outer wall integrally formed therewith and extending a height above the central recessed portion. The compressor valve plate assembly may additionally include a second valve plate including an outer perimeter portion abutting the outer wall of the first valve plate. 
         [0008]    The suction chamber may be defined between first and second valve plates. The second valve plate may include an inlet port in communication with the suction chamber. The second valve plate may include an outlet port in communication with the suction chamber. The first valve plate may include a support member integrally formed with and extending from the central recessed portion and engaged with the second valve plate. 
         [0009]    The support member may include a rib extending therefrom. The first and second valve plates may be brazed together. The second valve plate may be formed from a stamping process. The second valve plate may include a circumferentially outer surface mechanically engaged with a circumferentially inner surface of the outer wall of the first valve plate. 
         [0010]    The first valve plate may be made from a steel. The valve plate assembly may consist of a single cast valve plate. The single cast valve plate may be formed by a lost foam casting process. The lost foam casting process may include a mold formed from Mullite sand. The single cast valve plate may include an as-cast reed valve relief therein. The single cast valve plate may be made from a steel. The single cast valve plate may include a sand cleanout passage that facilitates removal of sand from internal passages of the single cast valve plate. 
         [0011]    In another arrangement, a monolithic compressor valve plate that separates a compressor head and a compressor body may include a first plate region defining a suction passage, a second plate region defining a discharge passage, and an outer wall extending between the first and second plate regions and defining a suction chamber in communication with the suction passage. The first and second plate regions may be disposed on opposite sides of the valve plate. 
         [0012]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0013]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0014]      FIG. 1  is a perspective view of a rotary compressor according to the present disclosure; 
           [0015]      FIG. 2  is a perspective exploded view of a first valve plate assembly; 
           [0016]      FIG. 3  is a perspective view of the first valve plate assembly of  FIG. 2 ; 
           [0017]      FIG. 4  is a perspective view of an alternate valve plate of the first valve plate assembly of  FIG. 2 ; 
           [0018]      FIG. 5  is a perspective exploded view of a second valve plate assembly; 
           [0019]      FIG. 6  is a perspective view of the second valve plate assembly of  FIG. 5 ; 
           [0020]      FIG. 7  is a perspective view of a third valve plate assembly; and 
           [0021]      FIG. 8  is a fragmentary section view of the compressor of  FIG. 1  including the valve plate assembly of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0023]    With reference to  FIGS. 1 and 8 , a compressor assembly  10  is shown and may generally be a reciprocating piston-type compressor. Compressor assembly  10  may include a compressor body  12 , a compressor head  14 , and a valve plate assembly  16  disposed therebetween. With reference to  FIGS. 2 and 3 , valve plate assembly  16  may include first and second valve plates  18 ,  20  brazed together. 
         [0024]    First valve plate  18  may include generally planar first and second surfaces  22 ,  24  having a series of suction inlet passages  26 , suction outlet passages  28 , and bolt holes  30  passing therethrough. As seen in  FIG. 8 , suction outlet passages  28  may selectively be in fluid communication with cylinders  31  of compressor assembly  10  through actuation of valves  33 , such as reed valves. Outlet passages  28  may form suction inlets for cylinders  31 . 
         [0025]    Second valve plate  20  may include first and second surfaces  32 ,  34  having discharge passages  36  and bolt holes  38  extending therethrough and spacers  40  extending therefrom. First surface  32  may include a recessed central portion  42  having a wall  44  extending therearound. Central recessed portion  42  may generally define a suction chamber within valve plate assembly  16 . The suction chamber may be in fluid communication with the inlet and outlet passages  26 ,  28 . First valve plate  18  may be formed from a stamping process and may be made of steel. Second valve plate  20  may be formed by investment casting and may also be made from steel. 
         [0026]    A casting mold may be made for second valve plate  20 . The mold may be made for either a solid investment process or a ceramic shell process. In either form, as second valve plate  20  is a cast part, each of the features discussed above that are associated with second valve plate  20  may be integrally formed with the entire second valve plate  20 . This may eliminate the need for multiple loose parts during assembly. Use of an investment casting may also provide for use of a higher carbon steel and improved heat treatment process relative to the currently used stampings. 
         [0027]    More specifically, use of investment castings may provide a greater control of chemistry variation of parts, providing a lower cycle time for a carburizing process. Steel used in conventional stampings may be provided from commercial steel mills. The steel provided by the commercial steel mills may include a range of chemistry variation that is significantly greater than the chemistry variation of the investment casting. This increased chemistry variation may result in use of a carburizing process with increased cycle times relative to cycle times associated with cast parts to ensure adequate hardness. 
         [0028]    With reference to  FIG. 4 , an alternate second valve plate  120  is shown. Second valve plate  120  may be generally similar to second valve plate  20 , with the exception of spacers  140 . Spacers  140  may include ribs  141  to increase the strength thereof relative to the non-ribbed spacers  40  of second valve plate  20 . The use of an investment casting process may generally provide for forming ribs  141 , as this type of geometry may not be formed using conventional stampings. 
         [0029]    With reference to  FIGS. 5 and 6 , an alternate valve plate assembly  216  may include first and second valve plates  218 ,  220 . First valve plate  218  may include generally planar first and second surfaces  222 ,  224  having a series of suction inlet passages  226 , suction outlet passages  228 , and bolt holes  230  passing therethrough. Second valve plate  220  may include first and second surfaces  232 ,  234  having discharge passages  236  and bolt holes  238  extending therethrough and spacers  240  extending therefrom. It is understood that spacers  240  may also include ribs (not shown) as discussed above. First surface  232  may include a recessed central portion  242  having a wall  244  extending therearound. Wall  244  may include first and second portions  246 ,  248 . Second portion  248  may be disposed radially outwardly of first portion  246  and may extend axially outwardly therefrom a distance generally equal to the thickness of first valve plate  218 . First valve plate  218  may be formed from a stamping process and may be made of steel. Second valve plate  220  may be formed by investment casting and may also be made from steel, similar to second valve plate  20 . 
         [0030]    However, rather than being brazed to one another, first and second valve plates  218 ,  220  may be connected through an interference fit engagement. More specifically, first valve plate  218  may have a length that is greater than the distance between opposite portions of second portion  248  of wall  244  and may be forced into engagement with second portion  248  of wall  244  of second valve plate  220 . First valve plate  218  may therefore be mechanically secured to second valve plate  220 . The mechanical, or interference fit, engagement between first and second valve plates  218 ,  220  may provide for the use of localized heat treatment options that may not be available with a brazed engagement. 
         [0031]    More specifically, rather than using a batch or oven-type heat treatment process associated with a brazed engagement, an individual localized heat treatment process may be used. The individual heat treatment process may be a laser or induction heat treatment process and may be applied to valve plate  220  at a region around discharge passages  236 . 
         [0032]    With reference to  FIG. 7 , an alternate valve plate  316  may be formed as a single piece. More specifically, valve plate  316  may be formed from a lost foam casting process. Valve plate  316  may be generally similar to valve plate assemblies  16 ,  216 , but may be formed from a single piece, rather than first and second valve plates. As such, the description of material properties and heat treatment options above applies equally to valve plate  316 . The lost foam casting process used to form valve plate  316  may utilize steel as the casting material. 
         [0033]    The use of the lost foam casting process may generally provide for easier design modifications relative to stamping or investment casting processes, since the sacrificial foam part is primarily the portion of the process that is altered for design modifications. Intricate passages, such as those found in valve plate  316 , may typically provide difficulty in removal of the sand typically used in the casting process. However, valve plate  316  may be cast using Mullite sand (Al 4.5 Si 1.5 O 9.5 ). Use of Mullite sand for the mold of valve plate  316  may generally provide for easier clean-out of valve plate  316  relative to traditional silica sands. 
         [0034]    In order to further facilitate sand clean-out after casting of valve plate  316 , several clean-out passages  312  may be cast into valve plate  316 . Additionally, as a result of the use of the lost foam casting process to form valve plate  316 , additional machining operations that may typically be required for stamping or investment casting processes may be eliminated. For example, reed valve relief  314  may be formed as-cast in valve plate  316 .
A compressor valve plate assembly includes a first valve plate formed of a unitary casting that separates a compressor head and a compressor body and defines a suction chamber receiving refrigerant at a suction pressure.