Abstract:
A hermetic rotary compressor assembly having a housing, a cylinder block and a bearing assembly within the housing. The cylinder block and the bearing assembly define a cylindrical cavity which has a roller piston disposed therein. The rotary compressor assembly includes a motor drivingly coupled to the roller piston and the cylinder block has a vane slot extending completely axially through and extending radially from an outside perimeter surface of the cylinder block to the cylindrical cavity. At least a portion of the vane slot is defined by a pair of substantially parallel sidewalls and a vane is disposed in and guided by the vane slot and is urged against said roller piston. The cylinder block is fixed in a state of circumferentially oriented stress. A method to assemble the rotary compressor includes spreading apart the sidewalls of the vane slot in the cylinder block, inserting into the spread apart slot a gauge vane of thickness greater than the thickness of a reciprocating vane, releasing the block to cause the slot sidewalls to engage the gauge vane, fixing the cylinder block to hold the engaged sidewalls, removing the gauge vane from the slot, and inserting the reciprocating vane in the slot, whereby a clearance is maintained between the reciprocating vane and slot sidewalls. Another method includes closing together sidewalls of the vane slot to engage the gauge vane, fixing the cylinder block to hold the engaged sidewalls, removing the gauge vane from the slot, and inserting the reciprocating vane in the slot.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is related to and claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application 60/088,754, filed Jun. 10, 1998. 
    
    
     BACKGROUND OF INVENTION 
     This invention pertains to hermetically sealed, positive displacement compressors for compressing refrigerant in refrigeration systems such as air conditioners, refrigerators and the like. In particular, the invention describes a rotary compressor mechanism of the type which includes a cylinder block having a cylindrical cavity, a bearing assembly and a motor assembly driving a roller piston disposed in the cylindrical cavity. More particularly, the cylinder block includes a vane slot extending completely axially through the cylinder block to accommodate a reciprocating vane therein and the vane being urged against the roller piston. 
     Rotary compressors are well known in the art, as exemplified by U.S. Pat. No. 4,889,475 which is assigned to assignee of the present application. Generally, the tolerances between the reciprocating vane and the slot sidewalls defining the vane slot of the cylinder block must be tightly controlled in order to optimize compressor efficiency. Proper vane clearances are necessary to allow free reciprocation of the vane in its slot and to allow sealing against discharge pressure gas blow-by therebetween. Maintaining these clearances in previous compressors often requires precision vane and/or slot machining, or select fitting of the individual vanes and cylinder blocks. A disadvantage arising from precision machining of the slot and/or vane is the associated cost of precision machining a pair of sidewalls defining the vane slot and vane. Always existent with precision machining is the immense cost associated with the act of “scrapping a part” when one of the final operations is spoiled due to a myriad of possible and easily made mistakes. A structure and method for easily providing uniform clearances between the vanes and their slots without resorting to costly and time consuming machining operations or select fitting is needed. 
     Generally, rotary compressor assembly entails first, laboriously preparing the vane and vane slot for an introduction of the vane into the vane slot, and second, the vane is introduced into the vane slot. A disadvantage, already mentioned hereinabove, is that laboriously preparing components, through precision machining and the like, has an increased cost associated therewith. Therefore, if components, such as the vane and vane slot, required less labor and the precise relationship required between the vane and vane slot were sustained through an inventive method of assembly, this inventive method would be highly desirous. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages of the prior art described above by providing a rotary compressor assembly as herein described. 
     The present invention rotary compressor assembly is hermetically sealed and comprises a housing, a cylinder block and a bearing assembly disposed within the housing. The cylinder block and the bearing assembly define a cylindrical cavity which has a roller piston disposed therein. The rotary compressor assembly includes a motor drivingly coupled to the roller piston. 
     The present invention rotary compressor assembly also includes the cylinder block having a vane slot extending completely axially through the cylinder block and extending radially from an outside perimeter surface of the cylinder block to the cylindrical cavity. At least a portion of the vane slot is defined by a pair of substantially parallel sidewalls and a vane is disposed in and guided by the vane slot and is urged against said roller piston. The cylinder block, of the present invention rotary compressor assembly, is in a state of circumferentially oriented stress and is fixed in that state of stress. 
     The present invention also includes a method to assemble a rotary compressor assembly which include steps, one step being, spreading apart the sidewalls of the vane slot in the cylinder block. Another step includes inserting into the spread apart slot a gauge vane of thickness greater than the thickness of a reciprocating vane. Yet another step includes releasing the block to cause the slot sidewalls to engage the gauge vane. Remaining steps include fixing the cylinder block to hold the sidewalls substantially parallel, removing the gauge vane from the slot, and inserting the reciprocating vane in the slot, whereby a clearance is maintained between the reciprocating vane and slot sidewalls. 
     The present invention also provides yet another method to assemble a rotary compressor assembly which includes steps, one being, inserting into the vane slot in the cylinder block the gauge vane of thickness greater than a thickness of the reciprocating vane. Another step includes closing together sidewalls of the vane slot in the cylinder block to cause the slot sidewalls to engage the gauge vane with the cylinder block. Also included are the steps of fixing the cylinder block to hold the sidewalls substantially parallel, removing the gauge vane from the slot, and inserting the reciprocating vane in the slot, whereby a clearance is maintained between the reciprocating vane and slot sidewalls. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a sectional side view of one embodiment of a compressor assembly according to the present invention, also showing the cross-over tube fluidly connecting the two discharge chambers and the compressor assembly discharge tube; 
     FIG. 2 is an enlarged fragmentary sectional side view of the rear portion of the compressor assembly shown in FIG. 1; 
     FIG. 3 is a sectional rear view of the compressor assembly shown in FIG. 2, taken along line  3 — 3  thereof; 
     FIG. 4 is a sectional front view of the compressor assembly shown in FIG. 2, taken along line  4 — 4  thereof; 
     FIG. 5 is a front view of the front main bearing of the compressor assembly shown in FIG. 1, including the outline of the cylinder block location on the axial main bearing surface; 
     FIG. 6 is a rear view of the main bearing shown in FIG. 5; 
     FIG. 7 is a rear view of the rear main bearing of the compressor assembly shown in FIG. 1, including the outline of the cylinder block location on the axial main bearing surface; 
     FIG. 8 is a front view of the main bearing shown in FIG. 7; 
     FIG. 9 is sectional side view of each of the main bearings shown in FIGS. 5 and 7, along lines  9 — 9  thereof; 
     FIG. 10 is a fragmentary sectional side view of each of the main bearings shown in FIGS. 6 and 8, along lines  10 — 10  thereof; 
     FIG. 11 is a front view of the common front and rear cylinder block of the compressor assembly shown in FIG. 1; 
     FIG. 12 is a front view of the front outboard bearing of the compressor assembly shown in FIG. 1; 
     FIG. 13 is a sectional side view of the outboard bearing of FIG. 12, along line  13 — 13  thereof; 
     FIG. 14 is a rear view of the rear outboard bearing of the compressor assembly shown in FIG. 1; 
     FIG. 15 is a sectional side view of the outboard bearing of FIG. 14, along line  15 — 15  thereof; 
     FIG. 16A is a partial sectional side view of the shaft of the compressor assembly shown in FIG. 1; 
     FIG. 16B is an enlarged sectional rear view of the shaft shown in FIG. 16A, along line  16 B— 16 B thereof; 
     FIG. 16C is an enlarged sectional front view of the shaft shown in FIG. 16A, along line  16 C— 16 C thereof; 
     FIG. 17A is an enlarged sectional side view of an eccentric of the compressor assembly shown in FIG. 1; 
     FIG. 17B is a sectional end view of the eccentric shown in FIG. 17A, along line  17 B— 17 B thereof; 
     FIG. 18 is a sectional side view of a second embodiment of a compressor assembly according to the present invention, also showing the cross-over tube fluidly connecting the two discharge chambers and the compressor assembly discharge tube; 
     FIG. 19 is an enlarged fragmentary sectional side view of the bottom portion of the compressor assembly shown in FIG. 18; 
     FIG. 20 is a sectional plan view of the compressor assembly shown in FIG. 19, taken along line  20 — 20  thereof; 
     FIG. 21 is a top view of the common upper and lower cylinder block of the compressor assembly shown in FIG. 18; 
     FIG. 22 a bottom view of the lower outboard bearing of the compressor assembly shown in FIG. 18; 
     FIG. 23 is a sectional side view of the outboard bearing of FIG. 22, along line  23 — 23  thereof; 
     FIG. 24 is a sectional side view of the third embodiment of a compressor assembly according to the present invention, also showing the cross-over tube fluidly connecting the two discharge chambers and the compressor assembly discharge tube; 
     FIG. 25 is an enlarged fragmentary sectional side view of the front portion of the compressor assembly shown in FIG. 24; 
     FIG. 26 is a sectional rear view of the compressor assembly shown in FIG. 25, taken along line  26 — 26  thereof; 
     FIG. 27 is a sectional front view of the compressor assembly shown in FIG. 25, taken along line  27 — 27  thereof; 
     FIG. 28 is a fragmentary perspective of a common cylinder block of the compressor assembly shown in FIG. 24, including the reed valve assembly and extended vane; 
     FIG. 29 is a front view of the front main bearing of the compressor assembly shown in FIG. 24, including the outline of the cylinder block location on the axial main bearing surface; 
     FIG. 30 is a rear view of the main bearing shown in FIG. 29; 
     FIG. 31 is a rear view of the rear main bearing of the compressor assembly shown in FIG. 24, including the outline of the cylinder block location on the axial main bearing surface; 
     FIG. 32 is a front view of the main bearing shown in FIG. 31; 
     FIG. 33 is sectional side view of each of the main bearings shown in FIGS. 30 and 32, along lines  33 — 33  thereof; 
     FIG. 34 is a front view of the common front and rear cylinder block of the compressor assembly shown in FIG. 24; 
     FIG. 35 is a sectional bottom view of the cylinder block of FIG. 34, along line  35 — 35  thereof; 
     FIG. 36 is a front view of the front outboard bearing of the compressor assembly shown in FIG. 24; 
     FIG. 37 is a sectional side view of the outboard bearing of FIG. 36, along line  37 — 37  thereof; 
     FIG. 38 is a sectional side view of the outboard bearing of FIG. 36, along line  38 — 38  thereof; 
     FIG. 39 is an exploded view of the pump assembly and rear outboard bearing of the present invention shown in FIG. 24; 
     FIG. 40 is a partial sectional side view of the shaft of the compressor assembly shown in FIG. 1; 
     FIG. 41 is an enlarged sectional rear view of the shaft shown in FIG. 40, along line  41 — 41  thereof; 
     FIG. 42 is an enlarged sectional front view of the shaft shown in FIG. 40, along line  42 — 42  thereof; 
     FIG. 43 is a front perspective view of an eccentric of the compressor assembly as shown in FIG. 24; 
     FIG. 44 is a sectional side view of the eccentric shown in FIG. 43, along line  44 — 44  thereof; 
     FIG. 45 is a sectional end view of the eccentric shown in FIG. 44, along line  45 — 45  thereof; 
     FIG. 46 is a sectional side view of a fourth embodiment of a compressor assembly according to the present invention, also showing the cross-over tube fluidly connecting the two discharge chambers and the compressor assembly discharge tube; 
     FIG. 47 is a sectional side view of a fifth embodiment of a compressor assembly according to the present invention, showing the suction tube fluidly connecting a discharge of one of the compressor mechanisms to a suction port of the remaining compressor mechanism and the compressor assembly discharge tube; 
     FIG. 48 is a sectional rear view of the compressor assembly shown in FIG. 47, taken along line  48 — 48  thereof; 
     FIG. 49 is a sectional rear view of the compressor assembly shown in FIG. 47, taken along line  49 — 49  thereof; 
     FIG. 50 is a simplified model of the common cylinder blocks of the compressor assemblies shown in FIGS. 1,  18 ,  24  and  46 - 47 , showing an inwardly tapered vane slot; 
     FIG. 51 is the model cylinder block of FIG. 51, showing a gauge vane therein, outward forces applied thereto and a state of circumferentially oriented tensile stress; 
     FIG. 52 is the model cylinder block of FIG. 51, showing an operable vane slot of width “S” and the state of circumferentially oriented tensile stress preserved therein; 
     FIG. 53 is a simplified model of the common cylinder blocks of the compressor assemblies shown in FIG. 1,  18 ,  24  and  46 - 47 , and an alternative to the model cylinder block of FIG. 51, showing an outwardly tapered vane slot; 
     FIG. 54 is the model cylinder block of FIG. 53, showing a gauge vane therein, inward forces applied thereto and a state of circumferentially oriented compressive stress; and 
     FIG. 55 is the model cylinder block of FIG. 53, showing an operable vane slot of width “S” and the state of circumferentially oriented compressive stress preserved therein. 
     Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplifications set out herein illustrate embodiments of the invention in alternative forms, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments disclosed below are not intended to be exhaustive or limit the invention to the precise form disclosed in the following detailed description. 
     Referring to FIG. 1, there is shown twin rotary compressor assembly  10 , a first embodiment according to the present invention. Compressor assembly  10  comprises housing  12  which is itself comprised of first housing portion  14 , second, cylindrical housing portion  16  and third housing portion  18 , first and third housing portions  14  and  18  being somewhat cup shaped, second housing portion  16  interposed between housing portions  14  and  18 . Compressor assembly  10  further comprises front and rear main bearings  20 ,  22 , respectively, which comprise, within housing portions  14  and  18 , respective front and rear compressor mechanisms  24  and  26 . As will be discussed further below, front main bearing  20  and rear main bearing  22  are mirror images of each other. Each of main bearings  20 ,  22  may be machined from a common casting or, alternatively, from a common sintered powder metal form. Main bearings  20  and  22  are respectively provided, at their peripheries, with annular, oppositely facing control surfaces  28  and  29 . Control surfaces  28  and  29  lie in parallel planes which are perpendicular to the central axis of each main bearing. The forwardly and rearwardly facing axial surfaces of cylindrical second housing portion  16  are each provided with axial counterbore  30  concentric about the central axis of housing portion  16  and which provides annular shoulders  31  against which axial surfaces  28 ,  29  abut. Shoulders  31  lie in parallel planes which are perpendicular to the central axis of cylindrical housing portion  16  and provide control surfaces for proper axial spacing and radial alignment of main bearings  20 ,  22 , and ensure they fit squarely within housing portion  16 . Proper placement of main bearings  20 ,  22  allows the shaft supported thereby to be properly journaled and assures proper clearances are provided between the moving components which comprise front and rear compressor mechanisms  24 ,  26 . The mating axial ends of housing portions  14 ,  16  and  18  are joined at the outer radial periphery of respective main bearings  20 ,  22 , to which they are sealably attached, as by welding. Welding each of housing portions  14 ,  16  and  18  to the main bearings separates housing  12  into three distinct internal chambers separated by the main bearings. Front chamber  32  is generally defined by inside surface  33  of housing portion  14  and forward facing axial surface  34  of main bearing  20 . Similarly, rear chamber  36  is defined by inside surface  37  of third housing portion  18  and rearward facing axial surface  38  of rear main bearing  22 . As will be discussed further below, chambers  32  and  36  contain refrigerant gas at discharge pressure, and are also referred to hereinafter as front and rear discharge chambers, respectively. Intermediate main bearings  20  and  22  and generally defined by inside cylindrical surface  39  of center housing portion  16  and surfaces  40  and  42  of front and rear main bearings  20  and  22 , respectively, is chamber  44 . Chamber  44 , as will be discussed further below, contains refrigerant gas at suction pressure, and is hereinafter referred to as suction chamber  44 . Within suction chamber  44  is disposed motor assembly  46  comprising stator  48  in surrounding relationship with rotor  50 . Shaft  52  extends through the center of rotor  50 , and is attached thereto to be driven by rotor  50  when motor assembly  46  is energized through terminals  54 , which electrically communicate the motor with an external source of power. Providing the motor in the suction chamber provides a cooler operating environment for it, promoting its efficient operation and prevents its overheating. Further, placement of the motor assembly in the relatively cool environment of the suction chamber provides for easier identification of an internal motor over-temperature condition vis-a-vis compressors having motors exposed to discharge pressure, for the temperature protection device (not shown) attached to the stator windings, which interrupts electrical current to the motor when it becomes overheated, need not be calibrated to operate in relatively narrow temperature difference ranges between discharge gas temperatures to which the motor is ordinarily exposed and the motor over-temperature point. 
     Shaft  52  comprises large diameter central portion  56 , which extends through rotor  50 , and forwardly and rearwardly extending small diameter portions  58  and  60 , respectively, adjacent portion  56 . At the juncture of shaft portion  56  with shaft portions  58  and  60 , shaft  52  is provided with annular groove  57  in which may be disposed oil seal  59  which may be made of a material such as Teflon® or Ryton® and past which some leakage is permissible. Annular shoulder  62  is formed on the axial surface of shaft large diameter portion  56 , at its juncture with groove  57 . Thrust washer  64  is disposed about small diameter shaft portion  60 , with its forwardly and rearwardly facing axial surfaces abutting shaft shoulder  62  and forward facing axial surface  66  of hub portion  68  of rear main bearing  22 . Motor assembly  46  is arranged such that the windings of stator  48  and rotor  50  are axially offset by distance δ. Upon energization of stator  48 , rotor  50  not only rotates but is also urged rearward as it attempts to axially align its windings with those of the stator. Rotor  50  thus exerts a rearward axial force on shaft  52  which is transferred through shoulder  62  to thrust bearing  64  and opposed by main bearing  22 . In this way, axial surfaces of the eccentrics and adjacent bearings are not brought into abutment and caused to carry an axial load. Small diameter shaft portions  58  and  60  are respectively journaled in main bearing journals  70  and  72 , which extend through main bearing hub portions  74  and  68 . 
     Front compressor mechanism  24  and rear compressor  26  are each provided with cylinder block  76 . Cylinder block  76  comprises outer peripheral surface  78  and inner cylindrical cavity  80 . Cylindrical cavity  80  extends through the width of cylinder block  76  between its forward and rearwardly facing parallel axial surfaces  82  and  84 , respectively. In front compressor mechanism  24 , cylinder block rearward surface  84  abuts forwardly facing axial surface  34  of main bearing  20 . Similarly, in rear compressor mechanism  26 , cylinder block forward surface  82  abuts rearwardly facing main bearing axial surface  38 . Thus it can be seen that cylinder blocks  76  are similarly oriented about shaft  52  in front and rear compressor mechanisms  24 ,  26 . 
     In front compressor mechanism  24 , forward cylinder block surface  82  abuts rearwardly facing axial surface  86  of front outboard bearing  88 . Outboard bearing  88 , frontmost cylinder block  76  and front main bearing  20  are attached by a plurality of bolts  90  extending through bolt holes  92 ,  94  and  96 , with bolts  90  threadedly engaging main bearing bolt holes  96 . In rear compressor mechanism  26 , rearward cylinder block surface  84  abuts forwardly facing axial surface  98  of rear outboard bearing  100 . As described above, a plurality of bolts  90  attaches outboard bearing  100 , rearmost cylinder block  76  and rear main bearing  22 , extending through bolt holes  102 ,  94  and  104  provided therein, threadedly engaging main bearing bolt holes  104 . Small diameter shaft portions  58  and  60  extend through outboard bearings  88  and  100 , and are supported in respective journals  106  and  108  provided therein. As will be discussed further below, front outboard bearing  88  and rear outboard bearing  100  are mirror images of one another, and may be machined together or on common tooling from identical castings or sintered powder metal forms. 
     Shaft  52  is provided with axial bore  110  which extends completely through its length. At its rearmost end, bore  110  is provided with impeller-type pump assembly  112  of a type commonly used in the art. Pump assembly  112  draws liquid lubricant from the lowermost portion of rear discharge chamber  36 , which serves as a sump, through vertical lubricant draw conduit or tube  114 , which extends downwardly from pump assembly  112 . The lowermost portion of front discharge chamber  32  also contains a quantity of liquid lubricant, also referred to as oil, as may that of suction chamber  44 . Pump assembly  112  provides oil through bore  110  to rear compressor mechanism  26  and to front compressor mechanism  24  for lubrication thereof, as will be discussed further below. 
     Discharge chambers  32  and  36  are in fluid communication with one another by means of external cross-over discharge conduit in the form of a tube  115  which extends axially along the outside of compressor housing  12  and, referring to FIGS. 3 and 4, extends into discharge chambers  32  and  36  to the extent that its open ends  116  are disposed above the normal height of a pool of liquid lubricant having surface level  118 . Cross-over tube  115 , as initially shown in FIG.  1  and various Figures thereafter, is an uninterrupted conduit, however, a sweat fitting or other like sealing fitting may disrupt the continuity to ease in the assembly process of the compressor assembly. Discharge pressure gas from front discharge chamber  32  is provided through cross-over tube  115  to discharge chamber  36 , wherein it joins the discharge pressure gas exhausted from rear compressor assembly  26  and is discharged from compressor assembly  10  through discharge conduit or tube  120 , which extends into the upper portion of rear discharge chamber  36 . Each pool of liquid lubricant having level  118  is maintained at approximately equal heights in both discharge chambers  32  and  36  by excess lubricant being redistributed between the two discharge chamber sumps via cross-over tube  115  as level  118  rises above the height of tube end opening  116  (FIG.  3 ). 
     Referring again to FIG. 1, it can be seen that each compressor mechanism  24  and  26  is provided with eccentric  122  mounted on respective small diameter shaft portion  58 ,  60  and disposed in cavity  80  of each cylinder block  76 . Each eccentric  122  is mounted about the axis of shaft  52  180° apart from the other to ensure proper balance. Further, counterweight  123  may be provided at opposite axial ends of rotor  50 , 180° apart, to aid in balancing compressor assembly  10 . Referring now to FIG. 4, which illustrates rear compressor mechanism  26  but which may be analogously applied to understand the structure of front compressor mechanism  24 , it can be seen that eccentric  122  is disposed about shaft portion  60  and is fixed for rotation therewith by means of set screw  124  threadedly engaged in hole  126  provided in the eccentric. Terminal point  128  of set screw  124  is received in countersink  130  provided in the surface of shaft portion  60 . With reference to FIGS. 2 and 4, it is shown that cylindrical roller piston  132  is provided about eccentric  122 , inside surface  133  of roller piston  132  in sliding contact with outer peripheral surface  134  of eccentric  122 . Further, it can be seen from FIGS. 1 and 2 that the forwardly and rearwardly facing axial surfaces of roller piston  132  are closely adjacent to the axial surfaces of the main and outboard bearings, with a maximum axial clearance preferably of about 0.0007 inch between the piston/bearing interfaces. In the known manner of operation of rotary compressors, roller piston  132  rotates on the cylindrical surface of cavity  80  in an epicyclic manner. Outer cylindrical surface  135  of roller piston  132  is in sliding contact with tip  136  of vane  138 . Vane  138  is provided in each compressor mechanism  24 ,  26 , and is urged into sliding engagement with roller piston surfaces  135  by means of springs  142  which encircle depending vane posts  144  and abuts vane surfaces  146  adjacent thereto. The opposite ends of springs  142  are retained by brackets  148  which are attached to surfaces  34  and  38  of main bearings  20  and  22  by means of rivets  150  provided in holes  152  and  154 . 
     Referring to FIGS. 2 and 4, it can be seen that vane  138  has opposite, parallel planar sides  156  and  158 , and opposite, parallel edges  160  and  162 . Edges  160 ,  162  are in sliding engagement with the respective adjacent axial main and outboard bearing surfaces. 
     Suction gases enter compressor assembly  10  through suction conduit or tube  164  (FIGS. 1,  3 ), which extends into suction chamber  44 . The outlet of suction tube  164  is covered by filter  165  in which debris carried by refrigerant returning to the compressor assembly may be captured. Filter  165  may be a wire cloth or finely meshed screen which may be spot welded over or press-fitted into the end of tube  164 . Filter  165  may be  100  mesh wire screen, comprising  100  interwoven wires of 0.007 inch diameter per inch, which would only allow particles smaller than approximately 0.003 inch to pass through to chamber  44 . Because the suction gases returning the compressor assembly are directed through suction tube  164  into chamber  44 , which provides a relatively large expansion volume, a refrigerant system incorporating the inventive compressor would not ordinarily require an in-line suction muffler external to the compressor assembly. 
     Suction chamber  44  will contain a quantity of lubricant carried with refrigerant returning to compressor  10 , and as shown in FIG. 1 and 2, lubricant level  166  is substantially lower than lubricant levels  118  in discharge chambers  32  and  36 . Referring to FIGS. 5-8, and  10 , it can be seen that front and rear main bearings  20 ,  22  are provided with suction ports  168 ,  170 , respectively, which extend axially therethrough (FIG.  10 ). Normally, suction chamber lubricant level  166  is below suction ports  168 ,  170  but may be above lubricant inlet bores  172 ,  174 , provided in respective main bearing surfaces  40 ,  42 . Bores  172 ,  174  extend axially from respective surfaces  40 ,  42  into web portion  175  of the main bearings, in which they terminate without projecting through to axial surfaces  34 ,  38  thereof. Referring to FIG. 10, radial conduits  176 ,  178  are provided in the peripheral edges of main bearings  20 ,  22  to fluidly connect lubricant intake bores  172 ,  174  with suction ports  168 ,  170 . The peripheral openings of conduits  176 ,  178  are sealed upon assembly and welding of housing portions  14 ,  18  to main bearings  20 ,  22 . 
     Suction ports  168 ,  170  communicate with suction port  180  in cylinder block  76  which can be seen in FIGS. 4 and 11. Like cylindrical cavity  80 , suction port  180  extends axially between the surfaces  82  and  84  of cylinder block  76 , and communicates directly with cavity  80  through suction inlet  182 . As suction gas flows from suction chamber  44  into suction port  180  through ports  168 ,  170 , it may aspirate oil from chamber  44  through lubricant intake apertures  172 ,  174  and bores  176 ,  178  into suction port  180 , if level  166  is above the height of apertures  172 ,  174 , thus scavenging oil from the suction chamber. This scavenged oil is carried by the refrigerant into cavity  80 , which comprises the compression chamber of compressor mechanisms  24 ,  26 , and delivered therethrough to discharge chambers  32 ,  36 . 
     In cylinder block  76 , adjacent suction inlet  182  is a vertically oriented channel or vane slot  184  which extends the width of the cylinder block between surface  82  and surface  84  and has generally parallel side walls  186 ,  188  (FIG.  11 ). Vane  138  is disposed in vane slot  184  and vertically reciprocates therein as its tip  136  follows outside surface  135  of roller piston  132 , with one of vane surfaces  156 ,  158  adjacent vane slot sidewall  186 , the opposite vane surface adjacent vane slot sidewall  188 . Vane  138  may be a sintered powder metal part, the tolerances between its opposite planar surfaces  156 ,  158  and its opposite edges  160 ,  162  closely controlled. Cylinder block  76  may be manufactured from individually cast blanks which have been machined or they may be sintered powder metal parts. Alternatively, an axially elongate “loaf” of uniform cross section may be produced by casting, powder metal techniques or extrusion, which is then sawed into individual cylinder blocks of appropriate thickness and machined. 
     An “off the shelf” cylinder block, including an inwardly tapered vane slot (FIG.  50 ), has a vane slot width less than the vane and requires a force being exerted, proximate to the vane slot walls, to force them apart to receive the vane. In order to provide proper clearances between vane slot sidewalls  186   a  and  188   a  and the adjacent vane surfaces  156 ,  158 , a process of assembling a rotary compressor according to the present invention includes the steps of: forcing apart vane slot walls  186   a  and  188   a  slightly; providing a dummy vane or gauge vane (FIGS. 51 and 54) having generally the same shape as vane  138  except being about 0.0020 inch thicker between its opposite planar surfaces in vane slot  184   a ; allowing vane slot walls  186   a ,  188   a  to resiliently come into contact with the planar sides of the gauge vane; assembling the main bearing, cylinder block and outboard bearing together about the shaft/eccentric/piston assembly; placing and torquing bolts  90  to appropriate levels to compress cylinder block  76   a  between the bearings, thereby establishing sufficient frictional contact between the abutting axial surfaces of the bearings and the cylinder block to hold vane slot walls  186   a ,  188   a  at their current spacing; and removing the gauge vane and substituting therefor vane  138 , which will have approximately 0.0020 inch clearance between one of its planar sides  156 ,  158  and its adjacent vane slot sidewall. 
     An alternative to the inwardly tapered vane slotted cylinder block, as hereinabove described, is an “off the shelf” cylinder block including an outwardly tapered vane slot (FIG.  53 ), having a vane slot width greater than the vane and requiring a force being exerted, proximate to the vane slot walls, to force them together to support the vane. A method of decreasing the width of vane slot  184   b  to provide a suitable clearance between the vane  138  and vane slot  184   b  may be employed. In order to provide proper clearances between vane slot sidewalls  186   b  and  188   b  and the adjacent vane surfaces  156 ,  158 , a process of assembling a rotary compressor according to the present invention includes the steps of: providing the gauge vane having generally the same shape as vane  138  except being about 0.0020 inch thicker between its opposite planar surfaces in vane slot  184   b ; decreasing the width of the vane slot  184   b  by forcing the vane slot walls  186   b  and  188   b  slightly together to frictionally hold the gauge vane therebetween; applying an inward force to the vane slot walls  186   b ,  188   b  to come into contact with the planar sides of the gauge vane; assembling the main bearing, cylinder block and outboard bearing together about the shaft/eccentric/piston assembly; placing and torquing bolts  90  to appropriate levels to compress cylinder block  76   b  between the bearings, thereby establishing sufficient frictional contact between the abutting axial surfaces of the bearings and the cylinder block to hold vane slot walls  186   b ,  188   b  at their current spacing; and removing the gauge vane and substituting therefor vane  138 , which will have approximately 0.0020 inch clearance between one of its planar sides  156 ,  158  and its adjacent vane slot sidewall. 
     Referring now to FIGS. 50-55, model cylinder blocks are disclosed, functionally appertaining to all the cylinder blocks disclosed herein, however, simplified to aid in the explanation of the relationship between the vane slot and the cylinder block of the present invention compressor assembly. Referring now to FIG. 50, shown is a model cylinder block  76   a  having a cylindrical cavity  80   a  defined by a cylinder wall  81   a . Also shown is tapered vane slot  184   a  cut all the way through the cylinder wall  81   a  and extending to an outer periphery  78   a  of the model cylinder block  76   a . The taper in tapered slot  184   a  has been exaggerated for clarity. Vane slot  184   a  is defined by a pair of vane slot sidewalls  186   a  and  188   a , respectively, and further includes a first vane slot opening  189   a , proximate to the outer periphery  78   a  of the model cylinder block  76   a , and a second vane slot opening  191   a , which is proximate to the cylinder wall  81   a  within the cylindrical cavity  80   a . FIG. 50 shows tapered vane slot  184   a  having the first vane slot opening  189   a , which is relatively narrower than the second vane slot opening  191   a , for reasons further described below. 
     FIG. 51 discloses the insertion of a gauge vane showing the model cylinder block  76   a  of FIG. 50, having a pair of equal and opposing forces  193  imparted on extended portions  185   a  of the cylinder block to elastically spread apart the vane slot sidewalls  186   a  and  188   a , respectively. A gauge vane  138   g  has been inserted between the vane slot sidewalls  186   a ,  188   a  and is shown holding the vane slot sidewalls  186   a ,  188   a  apart, and substantially parallel. The gauge vane  138   g  has first and second ends  139  and  140 , respectively, wherein the first end  139  of gauge vane  138   g  has a tapered contour so that the gauge vane may be forcefully wedged into the first vane slot opening  189 , which acts similar to forces  193  spreading apart the vane slot sidewalls  186   a ,  188   a , to fit the vane therebetween. With the gauge vane  138   g  in place and having vane slot sidewalls  186   a  and  188   a , respectively, in contact with the gauge vane  138   g , a state of stress develops in cylinder block portions  197   a  and is represented by arrows  195 . The state of stress  195  is circumferentially oriented about the cylinder block  76   a  and is disposed within cylinder block portions  197   a , which are located immediately adjacent cylinder wall  81   a , and continue circumferentially about the cylinder block  76   a . The state of stress  195  is tensile in nature and circumferentially orients therealong a substantial portion of cylinder block portions  197   a . State of stress  195  is caused by the spreading apart of vane slot sidewalls  186   a  and  188   a , respectively, and once created, the cylinder block  76   a  is secured by bolting or the like to an adjoining bearing or bearings, to preserve the stresses within cylinder block portions  197   a . Thus, once the gauge vane  138   g  is removed the state of stress  195  remains preserved therein, as hereinafter described. 
     Referring to FIG. 52, the model cylinder block  76   a  is shown having preserved the circumferentially oriented stress, as shown by arrows  195 , however, the gauge vane  138   g  has been removed and replaced by vane  138 . FIG. 52 shows, albeit exaggeratedly, a vane slot width “S” being preserved, with gauge vane  138   g  removed, and the state of circumferentially oriented stress  195  remaining preserved therein. The vane  138 , having a width or thickness “T”, is freely reciprocatable within vane slot width “S”, the width between “S” and “T” defines a clearance. In order for vane  138  to reciprocate within vane slot width “S” the clearance must be suitable, however, an excessive clearance leads to premature vane wear, and additionally, inefficient compressor mechanism operation due to refrigerant gas blow-by through the clearance. 
     Referring now to FIGS. 53-55, similar to FIGS. 50-52, a simplified cylinder block is shown, however the cylinder block has a closeable vane slot. Referring now to FIG. 53, shown is a model cylinder block  76   b  having a cylindrical cavity  80   b  defined by a cylinder wall  81   b . Tapered vane slot  184   b  is cut all the way through the cylinder wall  81   b  and extends to an outer periphery  78   b  of the model cylinder block  76   b . The taper in tapered slot  184   b  has been exaggerated for clarity. Vane slot  184   b  is defined by a pair of vane slot sidewalls  186   b  and  188   b , respectively and further includes a first vane slot opening  189   b , proximate to the outer periphery  78   b  of the model cylinder block  76   b , and a second vane slot opening  191   b , which is proximate to the cylinder wall  81   b  within the cylindrical cavity  80   b . FIG. 53 shows tapered vane slot  184   b , having the first vane slot opening  189   b , which is relatively broader than the second vane slot opening  191   b , for reasons further described below. 
     FIG. 54 represents the gauge vane insertion or vane slot setting step of the inventive method, showing the model cylinder block  76   b  of FIG. 53, having a pair of equal and opposing forces  199  imparted on extended portions  185   b  of the cylinder block  76   b  elastically closing together the vane slot sidewalls  186   b  and  188   b , respectively. A gauge vane  138   g  has been inserted between the vane slot sidewalls  186   b ,  188   b  and is shown contacting vane slot sidewalls  186   b ,  188   b  to provide a substantially parallel slot. Gauge vane  138   g  used on cylinder block  76   a , may also be utilized on cylinder block  76   b  in providing a standard in which to set the vane slot. With the gauge vane  138   g  in place and having vane slot sidewalls  186   b  and  188   b , respectively, in contact with the gauge vane  138   g , a circumferentially oriented state of stress  201  develops in cylinder block portions  197   b , which are located immediately adjacent cylinder wall  81   b . The cylinder block portions  197   b  are circumferentially continuous about the cylinder wall  81   b . The circumferentially oriented state of stress  201  is compressive in nature, for a substantial portion of cylinder block portions  197   b  about the cylinder wall  81   b . State of stress  201  is caused by the closing together of vane slot sidewalls  186   b  and  188   b , respectively, and once the stress  201  is created, the cylinder block  76  is thereafter secured by bolting or the like to an adjoining bearing or bearings, to preserve the stresses within the cylinder block portions  197   b . Thus, subsequent to the gauge vane  138   g  being removed the state of stress  201  is preserved therein, as hereinafter described. 
     Referring to FIG. 55, the model cylinder block  76   b  is shown having the gauge vane  138  removed and the gauge vane width “S” preserved. Also preserved is the circumferentially oriented compression stress  201 . FIG. 55 shows the vane  138   g  in the vane slot  184 . The vane  138   b  having a width or thickness “T” is freely reciprocatable within vane slot width “S” and the width between “S” and “T” defines a clearance. In order for vane  138  to reciprocate within vane slot width “S” the clearance must be suitable, however, an excessive clearance leads to excessive vane wear and malfunction. Also an excessive clearance coincides with inefficient compressor operation due to refrigerant gas blow-by through the clearance. 
     As mentioned above, during the step of increasing the width “S” of the vane slot  184   a , cylinder block portions  197   a  develop a state of circumferentially oriented tensile stress  195 , which is preserved once the cylinder block  76   a  is clamped between outboard bearings  88 ,  100  and main bearings  20 ,  22 . In contrast, during the step of decreasing the width “S” of the vane slot  184   b , cylinder block portions  197   b  develop a state of circumferentially oriented compressive stress  201 , which is preserved once the cylinder block is clamped between outboard bearings  88 ,  100  and main bearings  20 ,  22 . Generally, pre-stressing portions of the cylinder block  76 , as hereinabove explained, results in offsetting dynamic forces imparted on the cylinder block  76  by the rotating roller piston  132 , to enhance wear resistence and longevity of the cylinder block  76 . Furthermore, the tapered vane slotted cylinder block requires fewer machining operations and costly machining operations may be avoided. 
     Referring now to FIGS. 1,  2  and  4 , and more specifically the liquid lubrication of the vane and vane slot, each liquid lubricant pool having surface level  118  in discharge chambers  32 ,  36  is of sufficient height to immerse vane  138  in the pool of lubricant. Immersion of vane  138  in the lubricant seals the clearance between vane  138 , the sidewalls of vane slot  184  and the adjacent axial bearing surfaces against refrigerant blow-by from the compression chamber, as well as lubricates the vane surfaces. 
     Referring again to FIG. 4, it can be seen that cylindrical discharge opening  190  is provided in the cylindrical wall of cavity  80  adjacent vane slot  184 , on the opposite side thereof from inlet opening  182 . By providing cylindrical discharge opening  190  in the wall of cavity  80  adjacent vane slot  184 , rather than in the axial surface of the outboard bearing, an outlet port of unchanging area is provided for discharge gases to be exhausted from the compression chamber throughout the compression cycle, regardless of the roller piston position. Adjacent and downstream of cylindrical discharge opening  190  is frustoconical valve seat  192  on which the mating frustoconical surface of head  194  of poppet  196  seals. Poppet head  194  is urged into sealing contact with surface  192  by compression spring  198  disposed about poppet shaft  200 . One end of spring  198  abuts the underside of poppet head  194 ; its opposite end abuts disc  202 , which is cushioned by neoprene cushion  204  and disposed in pocket  206  of poppet retainer  208 . Retainer  208  limits the radial travel of poppet  196  away from seat  192  to about ⅛ inch, the terminal end of poppet shaft  200  opposite head  194  abutting disc  202  at the furthest extent of poppet travel. Neoprene cushion  204  softens the impact of the poppet shaft end against disc  202 , thereby quieting the operation of the compressor. Poppet  196  prevents previously exhausted discharge pressure gases from reentering the compression chamber, where they would otherwise be recompressed, undermining the efficiency of the compressor. Poppet  196  is preferably made of a durable yet lightweight material, for example a plastic such as Vespel™, as may retainer  208 . Disc  202  may be plastic or metal. 
     Retainer  208  is provided in radially extending cylinder block bore  210  and maintained in position therein by means of pin  212  extending through a pair of holes  214  provided on opposite axial sides of bore  210 . Pin  212  is prevented from moving axially within holes  214  by its ends abutting the adjacent axial surfaces of the main and outboard bearings. Discharge gases compressed in the compression chamber urge poppet  196  off its seat  192  against the force of spring  198  and flow past poppet head  194  into discharge cavity  216  provided in cylinder block  76 . Poppet  196  is urged by spring  198  back into sealing engagement with seat  192  once the discharge pressure gas has exited the compression chamber through opening  190 , preventing the expelled gas from flowing back into the compression chamber. 
     Discharge cavity  216  extends axially between cylinder block surfaces  82 ,  84 , and is defined by cavity surface  217  and the adjacent axial surfaces of the main and outboard bearings. Cavity  216  serves to attenuate gas-borne noises and pressure pulses arising from operation of the compressor. As shown in FIG. 4, discharge gases exit cavity  216  by means of discharge port  218  provided in outboard bearing  100  (and through corresponding port  220  in front outboard bearing  88 , FIG.  12 ). Discharge gases expelled from cylinder block discharge cavity  216  through discharge ports  218 ,  220  enter respective discharge chambers  32  and  36 . Those of ordinary skill in the art will appreciate that discharge chambers  32  and  36  serve as mufflers as well, attenuating gas-borne noises and pressure pulses before discharge pressure refrigerant exits compressor assembly  10  through discharge conduit or tube  120 . Furthermore, each compressor mechanism  24 ,  26 , respectively, draws refrigerant gases from the suction chamber  44  and discharges the compressed gases into the discharge chambers  32 ,  36  respectively, to further attenuate sources of fluid borne noise and vibration which would be otherwise carried by suction conduits, discharge conduits and the like, rigidly connecting the housing to the compressor mechanisms. 
     As shown in FIGS. 13 and 15, outboard bearings  88  and  100  are provided with conduits  222  and  224  which respectively extend from inlets  226 ,  228  to outlets  230 ,  232 . Inlets  226  and  228  are provided proximate the terminal ends of shaft  52  in respective bearing hub portions  234 ,  236 ; outlets  230 ,  232  open onto respective axial surfaces  86 ,  98  into regions of the compression chambers which are at a pressure intermediate suction and discharge pressure (FIG.  4 ). The outboard axial surfaces of roller pistons  132  cover and block outlets  230 ,  232  as the roller pistons reach orientations about the cylindrical surfaces of cavities  80  normally corresponding to pressures at and above which oil, which is approximately at discharge pressure, may be forced to reversibly flow backwards through conduits  222 ,  224 . Referring to FIG. 1, it can be seen that front outboard bearing hub portion  234  is provided with oil diverter cap  238 , which may be made of sheet metal. Cap  238  directs oil received from shaft bore  110  and directs it towards inlet  226  of conduit  222 . Through conduit  222  oil is provided to the compression chamber of the front compressor mechanism, lubricating exposed surfaces therein. Similarly, hub  236  of rear outboard bearing  100  is provided with cap  240  enclosing a portion of pump  112  and which may also be made of sheet metal. Cap  240  is provided with an central aperture through which lubricant draw conduit or tube  114  is fitted. Cap  240  directs lubricant received from lubricant tube  114  upstream of pump  112  through inlet  228  of conduit  224 . 
     FIGS. 16A through 16C detail the shaft  52 . As seen in FIG. 16B and 16C, at the point of respective small diameter shaft portions  60  and  58  about which eccentrics  122  are attached thereto. FIG. 16B shows that shaft portion  60  is provided with crossbore  242  which extends through the diameter of shaft portion  60  intersecting axial bore  110 . FIG. 16C shows that shaft portion  58  is provided with similar crossbore  244 . Referring now to FIGS. 17A and 17B, there is shown cross-sectional views of eccentric  122 , which as discussed above is attached to the shaft  52  at countersinks  130  provided in shaft portions  58  and  60 . Eccentric  122  is provided with axial bore  246  having centerline  248  offset and parallel to axis  250  of shaft  52  (FIG.  16 A). Eccentric  122  is provided with crossbore  252  which extends through eccentric bore  246  to a second axial bore  254  extending between the axial surfaces of the eccentric. With eccentric  122  assembled to shaft portions  58 ,  60 , eccentric crossbore  252  is brought into alignment with shaft crossbores  244  and  242 . Because one end of crossbore  252  opens to outside surface  134  of the eccentric, oil provided through bore  110  to aligned bores  242 ,  252  and  244 ,  252  lubricates the interfacing cylindrical surfaces  133  and  134  between roller piston  132  and eccentric  122 . The opposite end of crossbore  252  extends into axial eccentric bore  254 , providing oil received from shaft bore  110  axially into the forward and rear spaces provided between the eccentric axial surfaces and the adjacent axial surfaces of the main and outboard bearings, these spaces inside surface  133  of roller piston  132 ; during normal compressor operation, these spaces are filled with oil. 
     Referring now to FIG. 18, there is shown compressor assembly  10 ′, a second embodiment according to the present invention. Compressor  10 ′ is for the most part identical with compressor assembly  10 , except is adapted to be vertically oriented. Thus with respect to the preceding discussion, the forward compressor mechanism  24  is, in this second embodiment, referred to as upper compressor mechanism  24 ′. Similarly, with respect to the preceding discussion, rear compressor mechanism  26  is now lower compressor mechanism  26 ′. All previously discussed components of compressor assembly  10  are configured and carried over into compressor assembly  10 ′ in the same way except as distinguished hereinbelow. 
     Compressor assembly  10 ′, being vertically oriented, has a pair of pools of liquid lubricant having levels  118 ′ in each of its discharge chambers  32 ,  36 . The level of lubricant or oil  118 ′ in upper discharge chamber  32  is, in normal operation of compressor assembly  10 ′, above axial surface  86  of upper outboard bearing  88 ′. Thus vane  138  of upper compressor mechanism  24 ′ is, as described with respect to front and rear compressor mechanisms  24 ,  26  of compressor assembly  10 , immersed in oil. Oil may initially collect in the lower portion of suction chamber  44 , as shown in FIG. 18 having level  166 ′, however, the oil eventually aspirates through the suction port  170  (FIGS.  7  and  8 ), and commonly exhibits a negligible level therein. As described above, oil will be scavenged from chamber  44  through aperture  174  in lower main bearing  22 . Aperture  172  of upper main bearing  20  will draw suction pressure gas into port  168  instead of oil. As best seen in FIG. 19, oil draw tube  114 ′ extends downwardly from cap  240  to provide access to the oil in the lower portion of chamber  36 . Compressor assembly  10 ′ employs the same lubrication methods as described above, with the exception that, because vane  138  of lower compressor mechanism  26 ′ cannot be immersed in oil, additional lubrication providing means is provided. Referring to FIG. 21, there is shown cylinder block  76 ′ which is identical to cylinder block  76  with the exception that sidewalls  186 ,  188  of vane slot  184  are provided with scallops  256 ,  258 , respectively. These scallops have the shape of a circle segment and, as will be described further below, allow oil to be provided adjacent the planar sides of vane  138  in lower compressor mechanism  26 . Referring to FIG. 22, it is seen that lower outboard bearing  100 ′ is provided with an axially directed through bore  260  of size matching the circle which would be defined by scallops  256  and  258  in cylinder block  76 ′. Into bore  260  is press fitted second oil draw conduit or tube  262  which extends from the location approximate surface  98  of outboard bearing  100 ′ downwardly into the oil contained in the lower portion of chamber  36 . During operation of compressor assembly  10 ′, as vane  138  reciprocates in compressor mechanism  26 ′, the oil in chamber  36 , which is under discharge pressure, is drawn through oil draw tube  262  into scallops  256 ,  258 , sealing the gap between vane slot sidewalls  186 ,  188  and planar sides  156 ,  158  of the vane. Thus, it can be seen that oil forced or drawn upward through tube  262  lubricates and seals vane  138  in vane slot  184 . Upper compressor mechanism  24 ′ may utilize a common cylinder block  76 ′. Upper outboard bearing  88 ′, may be provided with bore  264  corresponding to bore  262  in lower outboard bearing  100 ′ to, perhaps, better facilitate machining operations. If upper outboard bearing  88 ′ is provided in compressor assembly  10 ′ instead of outboard bearing  88 , bore  264  would be plugged to prevent the ingress of discharge pressure gasses from chamber  32  into scallops  256 ,  258 . Bore  264  would be plugged with plug  266  (FIG.  18 ). 
     Referring to FIG. 24, a third embodiment of the twin rotary compressor assembly  10 ″ is shown and is similar to the first embodiment compressor assembly  10  except as identified hereinbelow. Refrigerant gases, at suction pressure, flow into tube  164 ″ through filter  165 ″ and into suction chamber  44 . Chamber  44 , as in the first embodiment, is the suction chamber wherein the motor assembly  46  is immersed in relatively cool refrigerant gases. Following introduction into suction chamber  44 , refrigerant then flows through identical suction mufflers  268 , fastened to front and rear main bearings  20 ″,  22 ″ respectively, as shown. Suction mufflers  268  are thin metallic or plastic discs, overlaying axial surface  40 ″ of the front bearing  20 ″ and surface  42 ″ of the rear bearing  22 .″ Suction mufflers  268  have collar portions  270 , which are slightly larger in diameter than hubs  68 ″ and  74 ″ to allow refrigerant gases to pass therebetween. Each suction muffler  268 , acts to slow down the refrigerant gases entering each compressor mechanism to alleviate and attenuate noise otherwise manifested by free flowing refrigerant gases. Similar to the operations of the first embodiment compressor assembly  10 , as previously described above, compressor assembly  10 ″ compresses refrigerant in compressor assemblies  24 ″ and  26 ″ and discharges the compressed gases into front discharge chamber  32  and rear discharge chamber  36  through front and rear outboard bearings  88 ″ and  100 ″, respectively. The discharge gases carrying fluid-borne noise are muffled by first housing portion  14 ″ and second housing portion  18 ″. Discharge gases within chamber  32 , as well as discharge gases from chamber  36 , communicate via external cross-over tube  115 ″. The merged discharge gases are then dispersed through the discharge tube  120 ″ exiting the housing  12 ″ of the compressor assembly  10 ″. 
     The compressor assembly  10 ″ supports shaft  52 ″ at two locations, namely, a front portion  282  and a rear portion  280 . At the front portion  282  of the shaft  52 ″, the supporting structure includes the front main bearing  20 ″ wherein the front main bearing  20 ″ includes a bushing  272  which contacts the large diameter portion  56 ″ of the front portion  282  of the shaft  52 ″. Likewise, at the rear portion  280  of the shaft  52 ″, the rear main bearing  22 ″ supports the shaft  52 ″ through rear bushing  274 . The shaft  52 ″ freely rotates within the front and rear bearings, however, endwise movement of the shaft  52 ″ is restrained by common cover plate  288 . Cover plates  288  mount to the front outboard bearing  88 ″ and the rear outboard bearing  100 ″, each secured by a pair of screws  292 , to restrain endwise movement of the shaft  52 ″. 
     Referring now to FIG. 25, orientation of shaft  52 ″, eccentric  122 ″ and roller piston  132 , and additionally, lubrication thereof, will now be discussed. The crossbore  252 ″ in eccentric  122 ″ aligns with the crossbore  244 ″ in the front portion  282  of the shaft  52 ″ to allow oil to flow to the roller piston  132 . Oil travels through bore  286 , down the centerline of the shaft  52 ″, entering crossbore  244 ″ and crossbore  252 ″ of eccentric  122 ″ to coat the inner surface  133  of the roller piston  132 . Eccentric  122 ″ includes a pair of reliefs  294  along the outer surface  134 ″ of the eccentric  122 ″ in order to increase oil flow to the inner surface  133  of the roller piston  132  as well as a pair of axial faces  295  of the eccentric  122 ″. Also shown is outboard bearing  88 ″ having an oil passageway  298 , well below oil level  118  so that vane  138 ″ reciprocating between vane slot surfaces  296  are well saturated in oil to prevent refrigerant gas blow-by. 
     Referring to FIG. 26, the outboard bearing  88 ″ includes a raised portion  234 ″, the discharge port  220 ″, and the oil passageway  298 . The raised portion  234 ″ of the outboard bearing  88 ″ also includes threaded holes  300  to fasten cover plates  288  thereto. Oil passage  298  in outboard bearing  88 ″ is shown well below oil level  118  allowing oil to enter passageway  298  and generally saturate vane  138 ″ and vane slot  184 ″ in oil. Discharge port  220 ″ is shown well above oil level  118  so that under normal operation of the front compressor mechanism  24 ″ oil does not create a back pressure and refrigerant gases may freely exit discharge port  220 ″. 
     Referring to FIG. 27, within the front compressor mechanism  24 ″ is shown the roller piston  132 , the eccentric  122 ″ and the shaft  52 ″ wherein the eccentric  122 ″ is pinned to the shaft  52 ″. The rear compressor mechanism  26 ″ involves an identical configuration in that the eccentric  122 ″ is thereby pinned to the shaft  52 ″. Momentarily referring to FIG. 42, there is seen a groove  306  in the shaft  52 ″ receiving a pin  302  (FIG. 27) and further, as shown in FIGS. 43-45 there is a groove  34  in the eccentric  122 ″ that receives the pin  302 , thereby securing the eccentric  122 ″ to the shaft  52 ″. 
     Referring again to FIG. 27, and more specifically the area about vane  138 ″, vane  138 ″ is shown in vane slot  184 ″ and held in contact with the roller piston  132  by biasing member or spring  142 ″. Spring  142 ″ is restrained within a spring cavity  308  by a cover  310  and cover  310  is secured by screw  312 . Screw  312  is threaded into hole  314  which is within cylinder block  76 ″. Scallops  256 ″ and  258 ″ can be seen disrupting spring cavity  308  as scallops  256 ″ and  258 ″ are continuous along the width of cylinder block  76 ″. Cylinder block  76 ″ includes an inner wall  313  defining a portion of the discharge cavity  216 ″ wherein a reed valve  318  and retainer  320  are secured. Reed valve  318  and retainer  320  operate by allowing compressed discharge gases to escape the cylindrical cavity  80 , and in addition, to keep discharge gas from flowing back into the cylindrical cavity  80 . The reed valve  318  and the retainer  320  are secured to the cylinder block  76 ″ by way of a pair of threaded fasteners  322 . 
     Referring to FIG. 28, the retainer  320  and the corresponding reed valve  318  include three individual fingers which correspond with three discharge openings  316  (FIG.  35 ). The retainer  320  has a first end  323  which is secured by fasteners  322  and a second end  325  including the three fingers extending therefrom. The three fingers of the retainer  320  overlay the three discharge openings  316 . Corresponding reed valve is sandwiched between the retainer  320  and inner wall  323 . Each finger of the retainer is held away from the inner wall  313  and acts as a stop for each corresponding finger of the reed valve  318 . Pressure within the cylindrical cavity  80  increases until the fingers of the reed valve are displaced and cylinder pressure is alleviated. The fingers of the reed valve  318  return to their original position overlaying the inner wall  313  when cylinder chamber pressure is sufficiently decreased. The retainer  320  may be made of a metallic material or a suitable rigid, high temperature plastic. The reed valve  318  may be made of a metallic material or a suitable high temperature polymer. Also shown in FIG. 28 are a pair of bolt holes  324  which receive bolts  336  to fasten cylinder block  76 ″ to the front main bearing  20 ″ and the rear main bearing  22 ″. 
     Referring now to FIG. 29, outboard bearing  20 ″ includes control surface  28 ″ which serves as a partition to separate discharge chamber  32  from suction chamber  44 . Main bearing  20 ″ includes the pair of holes  326  that receive the bolts  336  (not shown) to fasten the cylinder block  76 ″ to control surface  28 ″ of the main bearing  20 ″. The main bearing  20 ″ also includes three threaded holes  331  which receive three threaded fasteners or bolts  90  (not shown) to secure not only the cylinder block  76 ″ but the outboard bearing as well. Suction port  168 ″ is a continuous hole through bearing  20 ″ and aligns with the suction portion of cylinder block  76 ″. 
     Referring now to FIG. 30, the side opposing control surface  28 ″ of main bearing  20 ″ is shown including a well portion  328  and several raised portions thereon. Three distinct and equally radially displaced raised portions  330  include threaded holes  331  which receive bolts  90  (not shown) to clamp the cylinder block  76 ″ between the front main bearing  20 ″ and the front outboard bearing  88 ″ (not shown). A pair of raised portions  332  include a first set of threaded holes  324  to receive bolts  326  in mounting the cylinder block  76 ″ to the front main bearing  20 ″. A second set of threaded holes  335  are included in raised portions  332  and receive screws  334  (not shown) to hold the suction muffler  268  thereagainst. The final raised portion  338  also includes threaded hole  335  to secure the suction muffler  268  in a third location to the front main bearing  20 ″. The front main bearing  20 ″ also includes suction port  168 ″ aligning with the suction port  180 ″ of the cylinder block  76 ″ and bushing  272 , within the center portion of front main bearing  20 ″ and supporting shaft  52 ″. 
     Referring to FIG.  31  and front main bearing  20 ″ in FIG. 29, rear main bearing  22 ″ is a mirror image of  20 ″. Rear main bearing  22 ″ includes a control surface  29 ″ which encloses discharge chamber  36  and separates discharge chamber  36  from suction chamber  44 . Rear main bearing  22 ″ includes a pair of threaded holes  326  to secure cylinder block  76 ″, and in addition, three threaded holes  331  which fasten the rear outboard bearing  100 ″ to the rear main bearing  22 ″ sandwiching the cylinder block  76 ″ therebetween. The rear main bearing  22 ″ also includes a hole therethrough  170 ″ aligned within suction port  180 ″ of cylinder block  76 ″ to allow suction gases within chamber  44  to enter cylinder block  76 ″ in the rear compressor mechanism  26 ″. Referring now to FIG. 32, the rear main bearing  22 ″ is a mirror image of front main bearing  20 ″, as shown in FIG. 30, and its ‘structure’ and operation is similar thereto. Referring now to FIG. 33, rear main bearing  22 ″ includes through holes  331  to receive bolts  90  (not shown) fastening rear outboard bearing  100 ″ to rear main bearing  22 ″. A second hole  335  is shown, which does not continue through the width of the rear main bearing  22 ″. A portion of hole  335  is threaded to receive a fastener  334  to secure the suction muffler  268  to the axial surface  42 ″ of rear main bearing  22 ″. 
     Referring now to FIG. 34, a common cylinder block  76 ″ of the third embodiment is shown. The vane slot  184 ″ includes an upper portion  340  and a lower portion  342 . The upper portion  340  of the vane slot  184 ″ includes the surfaces  186 ″ and  188 ″ contacting the vane  138 ″, whereas during compressor assembly  10 ″ operation, the lower portion  342  of the vane slot  184 ″ does not contact vane  138 ″. The upper portion  340  of the vane slot  184 ″ is separated from the lower portion  342  by scallops  256 ″ and  258 ″, respectively. Cylinder block  76 ″ includes holes  94  which facilitate outboard bearing bolts  90  (not shown) and additionally, holes  324  to facilitate cylinder block screws  334  (not shown). 
     Referring to FIG. 35, cylinder block  76 ″ includes the inner wall  313  partially defining the discharge cavity  216 ″ which accommodates the retainer  320  and reed valve  318 . More specifically, a pair of holes  344  include threads which receive a pair of screws  322  (FIG. 28) to secure the retainer  320  and reed valve  318 . Also, within inner wall  313  are three discharge openings  316  which fluidly connect discharge cavity  216 ″ to cylindrical cavity  80 . Discharge openings  316  in inner wall  313  are overlayed by the three fingers of the reed valve  318  (FIG.  28 ). Cylinder block  76 ″ also includes a spring cavity having a suitable depth to receive an adequate sized spring, such as spring  142 ″ (FIG.  27 ), however leaving enough cylinder block material to form an adequately supportive vane slot for the vane  138 ″. 
     Referring to FIGS. 36-38, there is shown the front outboard bearing  88 ″ and more specifically the oil conduit  224 ″ contained therein. FIG. 37 displays oil conduit  224 ″ having a conduit inlet  226 ″ at chamfer  346  extending diagonally through the width of the outboard bearing  88 ″, and exiting at conduit outlet  230 ″ of the axial surface  86 ″. Conduit outlet  230 ″ is positioned within an interior portion of the cylindrical cavity  80  to expose front portion  282  of shaft  52 ″ to a lower pressure than rear portion  280  of shaft  52 ″. This pressure difference acts to draw oil from rear portion  280  of shaft  52 ″ to front portion of shaft  52 ″ through bores  284  and  286 , respectively (FIG.  24 ). This “rear to front” migration of oil through shaft  52 ″ ensures oil is introduced into cylindrical cavities  80  for proper lubrication of the roller piston  132 ″ and surfaces defining the cylindrical cavity  80 . FIG. 38 displays the pair of holes  300  which threadably receive screws  292  to secure cover plate  282  in restraining endwise movement of shaft  52 ″. 
     Referring to FIG. 39, rear outboard bearing  100 ″ is shown with the oil pump assembly  112 ″. Rear outboard bearing  100 ″ includes two through holes: the oil passageway  298  and discharge port  218 ″. Referring now to FIGS. 40-42, shaft  52 ″ includes the front portion  282  and the rear portion  280  coinciding with the front and rear ends of the compressor assembly  10 ″. A center portion of the shaft includes a surface  56 ″ which is in rotational contact with the front bushing  276  and the rear bushing  278 . On shaft  52 ″ are a pair of O-ring grooves  276  and  278 , respectively, which receive O-rings (not shown). O-ring grooves  276  and  278 , respectively, serve to separate the suction chamber pressure within suction chamber  44  from the discharge chamber pressure in front chamber  32  and rear discharge chamber pressure in rear chamber  36 . Shaft  52 ″ includes a large diameter inner bore  286  and a somewhat smaller bore  284  extending through the rear portion  280  of the shaft  52 ″. Cross bore  242 ″ allows oil, being drawn from the rear portion  280  of the shaft, into eccentric  122 ″, similarly, cross bore  244 ″ allows oil being drawn from the rear portion  280  of the shaft  52 ″ and into eccentric  122 ″ positioned at the front portion  282  of the shaft  52 ″. 
     Referring to FIG. 41, crossbore  242 ″ is shown intersecting through bore  284  to facilitate the migration of oil into eccentric  122 ″. Also shown is surface  60 ″ including a disruption thereon in the form of a pin groove  350 . Referring to FIG. 42, the front portion  282  of the shaft  52 ″ includes outer surface  56 ″, front small diameter portion  58 ″ and pin groove  306  thereon. Crossbore  244 ″ intersects inner bore  286  to welcome oil migration into the eccentric  122 ″ attached thereto (not shown). 
     Referring now to FIGS. 43-45, eccentric  122 ″ includes a pair of reliefs  294  and inner bore  246 ″ formed continuously through and a pin groove  304  therealong. During operation of the compressor  10 ″, oil moves through passageway  252 ″ towards the outer surface  134 ″ of eccentric  122 ″ coating the outer surface  134 ″ as well as the inner surface  133  of the roller piston  132 . The pair of reliefs  294  facilitate optimum lubrication of axial faces  295  of the eccentric  122 ″. 
     Referring now to FIG. 46, a fourth embodiment of the compressor assembly  10 ′″ of the present invention is shown and is similar in many aspects to the third embodiment  10 ″, however, vertically oriented. The compressor assembly  10 ′″ includes a lower compressor mechanism  26 ′″ having an oil suction tube  262 ″ sealably fitting into an oil passageway  353  in lower outboard bearing  100 ″ to draw from oil level  118 ″ and lubricate the vane  138 ′″. Also included in this particular embodiment is an elbowed pump intake conduit in the form of a tube  354  within the oil pump assembly  112 ′″ to draw oil vertically and into the lower portion  280  of the shaft  52 ′″. The oil level in the upper discharge chamber, nearing the discharge port, becomes an undesirous source of backpressure if such level exceeds the discharge port, however, nonetheless depicted to set forth that the reed valve  318  (FIG.  28 ), within the cylinder block, may suffice as an oil barrier to block excessive amounts of oil attempting to enter the cylindrical cavity via the discharge port. 
     Referring to FIG. 47, yet another embodiment, the fifth embodiment of the present invention compressor assembly  10 ″″, discloses a cascaded compressor assembly, or series configuration, such that general operation can be described as follows: a first compressor mechanism  24 ″″ compresses refrigerant gas to an intermediate pressure stage and discharges such pressurized gas to a second compressor  26 ″″, via an suction tube  356 , wherein the final discharge pressure is obtained. More specifically, refrigerant gas is introduced at a suction pressure within suction chamber  44  and thereafter is suctioned into front compressor  24 ″″, exclusively. The gas at suction pressure is then compressed to an intermediate pressure and dispersed within discharge chamber  32 . Thereafter, the refrigerant gas at intermediate suction pressure and within discharge chamber  32  is extended through suction tube  356 . Suction tube  356  is in exclusive communication with an suction port  358  located on an axial surface  359  of the outboard bearing  100 ″″ of the rear compressor mechanism  26 ″″. The intermediate stage refrigerant gas, supplied to compressor  26 ″″ by suction tube  356 , is further compressed and discharged into discharge chamber  36 . The discharged refrigerant, at the secondary or maximum pressure, within chamber  36  exits the compressor housing  12 ″″ through discharge tube  120 ″″. 
     Referring to FIG. 48, the rear outboard bearing  100 ″″ has an suction port  358 , sealably receiving the suction tube  356 , the oil passageway  298 ″″ and the discharge port  218 ″″. Once again, oil level  118 ″″ substantially covers the vane  138 ″″ and vane slot  134 ″″ (see also FIG.  47 ). However, it can be seen care is taken to avoid oil level to reach discharge port  218 ″″. Suction port  358  seals around suction tube  356  therefore an oil level  118 ″″ substantially thereover the suction port  358  will not hinder operation of the compressor assembly  10 ″″ whatsoever. Referring to FIG. 49, main bearing  22 ″″ has control surface  29 ″″ with cylinder block  76 ″″ attached thereto. However, in contrast to the previously hereinabove described compressor assembly embodiments, compressor assembly  10 ″″ includes the main bearing  22 ″″ which does not fluidly communicate with the suction chamber  44 . 
     While this invention has been described as having exemplary designs, the present invention may be further modified within the spirit and scope of this disclosure. Therefore, this application is intended to cover any variations, uses, or adaptations of the invention using its general principles. For example, aspects of the present invention may be applied to single cylinder rotary compressors. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.