Abstract:
A valve plate assembly for a compressor includes a first plate and a second plate disposed between and providing communication between a compressor head and a compressor body. The first and second plates are separated by a spacer supporting a load approximately centrally relative to the first and second plates.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 10/374,385 filed on Feb. 25, 2003. The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to refrigeration compressors. More particularly, the present invention relates to a reciprocating piston type refrigeration compressor which incorporates a unique design for the valve plate assembly which improves the clamping characteristics of the valve plate gasket and thus improves the sealing of the valve plate gasket. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Reciprocating piston type compressors typically employ suction and discharge pressure actuated valving mounted onto a valve plate assembly which is located at the end of a cylinder formed by a compressor body. The valve plate assembly is typically sandwiched between a compressor head and the compressor body. A valve plate gasket is located between the valve plate assembly and the compressor body to seal the interface. 
     Traditionally, the valve plate gasket is compressed due to a clamping load which is created by the attachment of the compressor head to the compressor body. The compressor head is attached to the compressor body by head bolts which extend through the compressor head, through the head gasket, through the valve plate assembly through the valve plate gasket and finally threadingly received by the compressor body. As these head bolts are tightened, compression of the valve plate gasket occurs. 
     Typically, the head bolts are located around the outside perimeter of the compressor head, the valve plate assembly and the valve plate gasket. Thus, the valve plate gasket receives most of its clamping load from this outside perimeter. Because the clamping load is generated at the outside perimeter of the valve plate gasket, there is a lower clamping load and thus a lower amount of compression of the valve plate gasket in the center portion of the valve plate gasket spaced from the outside perimeter. Because of this lower amount of compression of the valve plate gasket in the center portion, most of the valve plate gasket failures occur in this center portion. 
     In addition to compression of the valve plate gasket by the head bolts, valve plate gasket compression load is also created by the high pressure discharge gas located above the valve plate assembly. This high pressure discharge gas presses the valve plate assembly against the valve plate gasket and the compressor body. Typically the valve plate assembly is comprised of an upper valve plate, a lower valve plate and one or more spacers located between the upper and lower valve plates. In the center area of the valve plate assembly, there is no head bolt as described above and thus there is no spacer which creates an open void due to the lack of a spacer between the upper and lower valve plates. This means that the load, exerted by the high pressure discharge gas, is exerted on the upper valve plate and this exerted pressure is not transmitted directly to the lower valve plate in this center portion. 
     The present invention provides the art with a unique valve plate assembly which improves the valve gasket clamping load in the center portion and thus it significantly reduces valve gasket failures. The unique valve plate assembly of the present invention includes a center spacer which is located between the upper and lower valve plates in the center portion of the valve plate assembly. By incorporating this additional center spacer, the valve plate assembly exerts an increased clamping force in this center portion to increase the compression of the valve plate gasket and thus improve its performance and durability. 
     In the first embodiment of the present invention, the center spacer defines a bolt hole which extends through the spacer. A center bolt is assembled through the valve plate assembly using this bolt hole and it is threadingly received by the compressor body. When this center bolt is tightened, it provides additional clamping load to the valve plate gasket in the center portion to produce a more even clamping load throughout the entire valve plate gasket to improve performance and durability while reducing failures. The center bolt can extend only through the valve plate assembly and through the valve plate gasket into the compressor body or the center bolt can extend through the compressor head, through the valve plate assembly and through the valve plate gasket into the compressor body if desired. 
     In another embodiment of the present invention, the center spacer does not include the bolt hole. The center spacer is located within the center portion of the valve plate assembly to transmit both the clamping load and the pressure exerted by the high pressure discharge gas from the upper valve plate, to the lower valve plate, to the valve plate gasket and finally to the compressor body. This additional load exerted onto the valve plate gasket at its center portion increases the compression of the gasket at the center portion to produce a more even clamping load throughout the entire valve plate gasket to improve performance and durability while reducing failures. This additional embodiment is useful when it is not possible to assemble a center bolt due to a compressor unloader system or other features of the compressor being located at a position which limits access to the center portion of the valve plate assembly. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a side view of a compressor assembly incorporating the unique valve plate assembly in accordance with the present invention; 
         FIG. 2  is a top view of the compressor assembly illustrated in  FIG. 1 ; 
         FIG. 3  is a partial cross-sectional view through the compressor assembly illustrated in  FIGS. 1 and 2  where each cylinder is shown rotated 90° about a central axis; 
         FIG. 4  is a top plan view of the unique valve plate assembly illustrated in  FIG. 1-3 ; 
         FIG. 5  is a side cross-sectional view of the unique valve plate assembly illustrated in  FIG. 4 . 
         FIG. 6  is a partial cross-sectional view similar to  FIG. 3  through a compressor assembly in accordance with another embodiment of the present invention; and 
         FIG. 7  is a side cross-sectional view of a unique valve plate assembly in accordance with another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. There is shown in  FIGS. 1-5  and compressor assembly  10  which incorporates the unique valve plate assembly in accordance with the present invention. Compressor assembly  10  comprises a compressor body  12 , a compressor head  14 , a head gasket  16 , a valve plate assembly  18  and a valve plate gasket  20 . 
     Compressor body  12  defines a pair of compression cylinders  22  within which a piston  24  is slidably disposed. Each compression cylinder  22  is in communication with both a discharge chamber and a suction chamber through valve plate assembly  18 . 
     Valve plate assembly  18  comprises an upper valve plate  26 , a lower valve plate  28 , an annular spacer  30  a plurality of interior spacers  32  and a center spacer  34 . Valve plate assembly  18  defines a pair of suction passages  36  which are in communication with the suction chamber of compression assembly  10  and a pair of discharge passages  38  which are in communication with the discharge chamber of compressor assembly  10 . Each discharge passage  38  is defined by a radially inclined or beveled sidewall  40  extending between an upper surface  42  and a lower surface  44  of valve plate assembly  18 . Beveled sidewall  40  is formed from upper valve plate  26 . A surface  46  of beveled sidewall  40  provides a valve seat for a discharge valve member  48  which is urged into sealing engagement therewith by discharge gas pressure and a spring  50  extending between discharge valve member  48  and a bridge-like retainer  52 . 
     As shown, discharge valve member  48  is of a size and a shape relative to discharge passage  38  so as to place a lower surface  54  thereof in substantially coplanar relationship to lower surface  44  of valve plate assembly  18 . Spring  50  is located in a recess  56  provided in retainer  52 . Discharge valve member  48  is essentially pressure actuated and spring  50  is chosen primarily to provide stability and also to provide an initial closing bias or preload to establish an initial seal. Other types of springs, other than that illustrated may of course be used for this purpose. Retainer  52 , which also serves as a stop to limit the opening movement of valve member  48  is secured to valve plate assembly  18  by a pair of suitable fasteners  58 . 
     Annular spacer  30  is disposed between upper valve plate  26  and lower valve plate  28  and annular spacer  30  forms suction passage  36  with upper valve plate  26  and lower valve plate  28 . The plurality of interior spacers  32  are positioned around each compression cylinder  22  as illustrated in  FIG. 4 . Valve plate assembly  18  is secured to compressor body  12  when compressor head  14  is secured to compressor body  12 . Valve plate assembly  18  is sandwiched between compressor head  14  and compressor body  12  with valve plate gasket  20  being sandwiched between valve plate assembly  18  and compressor body  12  and head gasket  16  being sandwiched between valve plate assembly  18  and compressor head  14 . 
     A plurality of bolts  60  extend through compressor head  14 , head gasket  16 , upper valve plate  26  of valve plate assembly  18 , annular spacer  30  of valve plate assembly  18 , lower valve plate  28  of valve plate assembly  18 , valve plate gasket  20  and are threadingly received by compressor body  12 . The tightening of bolts  60  compresses valve plate gasket  20  to provide a sealing relationship between valve plate assembly  18  and compressor body  12  provide a sealing relationship between valve plate assembly  18  and compressor head  14 . As shown in the Figures, the plurality of bolts  60  and annular spacer  30  of valve plate assembly  18  are located around the outer circumferential portion of compressor head  14  and valve plate assembly  18 . In the prior art, the plurality of bolts  60  extending through compressor head  14 , head gasket  16 , valve plate assembly  18 , valve plate gasket  20  and threadingly received by compressor body  12  were the only mechanical means for providing a compressive load to valve plate gasket  20 . While this compressive load was sufficient for the outer circumferential portion of valve plate gasket  20 , the center portion of valve plate gasket  20  would see less of a compressive load than the outer circumferential portion due to the distance between the center portion and each of the plurality of bolts  60 . 
     The present invention improves the compressive characteristics of valve plate gasket  20  and thus its performance and durability by adding center spacer  34 . Center spacer  34  is located at approximately the geometric center of valve plate assembly  18  at a position which is on a line which extends between the geometric center of one compression cylinder  22  and the geometric center of an adjacent compression cylinder  22 . This places center spacer  34  generally midway between both the length and width of valve plate assembly  18 . Center spacer  34  extends between upper valve plate  26  and lower valve plate  28  and is received within a bore  62  defined by lower valve plate  28 . While illustrated as being received in bore  62  in lower valve plate  28 , bore  62  could be located in upper valve plate  26  and center spacer  34  could be reversed from what is illustrated if desired. Center spacer  34  defines a through hole  64  which is aligned with a hole  66  extending through upper valve plate  26 . A center bolt  68  extends through hole  66  of upper valve plate  26 , through hole  64  of center spacer  34  and is threadingly received in compressor body  12 . The tightening of center bolt  68  provides additional compressive load for valve plate gasket  20  at the center of valve plate gasket  20  to increase the compression of valve plate gasket  20 , to produce a more even clamping load throughout the entire valve plate gasket  20  and to improve both the performance and durability of its sealing function. 
     Valve plate assembly  18  further defines an annular valve seat  70  and sidewall  40  defines an annular valve seat  72  located at its terminal end. Disposed between valve seat  70  and valve seat  72  is suction passage  36 . 
     Valve seat  72  of sidewall  40  is positioned in coplanar relationship with valve seat  70  of valve plate assembly  18 . A suction reed valve member  76  in the form of an annular ring sealingly engages, in its closed position, valve seat  72  of sidewall  40  and valve seat  70  of valve plate assembly  18  to prevent passage of fluid from compression cylinder  22  into suction passage  36 . A central opening  78  is provided in suction reed valve member  76  and is arranged coaxially with discharge passage  38  so as to allow direct fluid flow communication between compression cylinder  22  and lower surface  54  of discharge valve member  48 . Suction reed valve member  76  also includes a pair of diametrically opposed radially outwardly extending tabs  80 . One tab  80  is used to secure reed valve member  76  to valve plate assembly  18  using a pair of drive studs  82 . 
     As piston  24  within compression cylinder  22  moves away from valve plate assembly  18  during a suction stroke, the pressure differential between compression cylinder  22  and suction passage  36  will cause suction reed valve member  76  to deflect inwardly with respect to compression cylinder  22 , to its open position (shown in dashed lines in  FIG. 3 ), thereby enabling gas flow from suction passage  36  into compression cylinder  22  between valve seats  70  and  72 . Because only tabs  80  of suction reed valve member  76  extend outwardly beyond the sidewalls of compression cylinder  22 , suction fluid flow will readily flow into compression cylinder  22  around substantially the entire inner and outer peripheries of suction reed valve member  76 . As a compression stroke of piston  24  begins, suction reed valve member  76  will be forced into sealing engagement with valve seat  70  and valve seat  72 . Discharge valve member  48  will begin to open due to the pressure within compression cylinder  22  exceeding the pressure within discharge passage  38  and the force exerted by spring  50 . The compressed gas will be forced through central opening  78 , past discharge valve member  48  and into discharge passage  38 . The concentric arrangement of valve plate assembly  18  and reed valve member  76  allow substantially the entire available surface area overlying compression cylinder  22  to be utilized for suction and discharge valving and porting, thereby allowing maximum gas flow both into and out of compression cylinder  22 . 
     The continuous stroking of piston  24  within compression cylinder  22  continuously causes suction reed valve member  76  and discharge valve member  48  to move between their open and closed positions. Compressor body  12  includes an angled or curved portion  84  at the outer edge of compression cylinder  22  adjacent the free end of suction reed valve member  76  to provide a friendly surface for suction reed valve member  76  to bend against, thereby significantly reducing the bending stresses generated within the free end tab  80 . 
     Referring now to  FIG. 6 , a compressor assembly  110  in accordance with another embodiment of the present invention is illustrated. The embodiment illustrated in  FIG. 6  is the same as the embodiment illustrated in  FIG. 3  except that center bolt  68  has been replaced by center bolt  168 . Center bolt  68  extended through valve plate assembly  18  and valve plate gasket  20  and was threadingly received by compressor body  12 . Center bolt  168  illustrated in  FIG. 6  extends through cylinder head  14 , valve plate assembly  18  and valve plate gasket  20  and is threadingly received by compressor body  12 . In order to exert the addition compressive loads, an extension  170  is added to cylinder head  14  through which center bolt  168  extends. The operation, function and features of compressive assembly  110  are the same as those described above for compressor assembly  10 . 
     Referring now to  FIG. 7 , a valve plate assembly  118  in accordance with another embodiment of the present invention is illustrated. Valve plate assembly  118  is the same as valve plate assembly  18  except that center spacer  34  has been replaced with center spacer  134 . Center spacer  134  is located at the same position as center spacer  34  which is at approximately the geometric center of valve plate assembly  118 . This places center spacer  134  generally midway between both the length and width of valve plate assembly  118  or the same position as shown for center spacer  34  in  FIG. 4 . Center spacer  134  extends between upper valve plate  26  and lower valve plate  28  and is received within a bore  162  defined by upper valve plate  26 . While illustrated as being received in bore  162  in upper valve plate  26 , bore  162  could be located in lower valve plate  28  and center spacer  134  could be reversed from what is illustrated if desired. 
     Because center spacer  134  is a solid member, center bolt  68  or  168  are not included and thus valve plate gasket  20  does not receive additional compression at its center portion through the tightening of a center bolt. Instead, the additional compressive load applied to the center portion of valve plate gasket  20  is applied by the addition of a center rib similar to extension  170  illustrated in  FIG. 6  and by gas pressure from compressed gas which is located in the gas discharge chamber located above valve plate assembly  118 . Compressed gas at discharge pressure exerts a load on upper valve plate  26  and this load is transferred directly to lower valve plate  28  through center spacer  134 . In addition, the tightening of bolts  60  exert a load on upper valve plate  26  through the center rib (not shown) and this load is also transferred directly to lower valve plate  28  through center spacer  134 . The exerted load on lower valve plate  28  is then exerted on valve plate gasket  20  to provide additional compressive load for valve plate gasket  20  at the center of valve plate gasket  20  to increase the compression of valve plate gasket  20 , to produce a more even clamping load throughout the entire valve plate gasket  20  and to improve both the performance and durability of its sealing function. In the prior art where center spacer  134  is not present, the pressure load exerted on upper valve plate  26  is not directly transferred to lower valve plate  28 . 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.