Patent Publication Number: US-6336797-B1

Title: Oiless rotary scroll air compressor air inlet valve

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application is directed to similar subject matter as is disclosed in the following U.S. Patent Applications: 
     “Oiless Rotary Scroll Air Compressor Crankshaft Assembly”, U.S. patent application Ser. No. 09/584,324, filed on Jun. 1, 2000 by Michael V. Kazakis and Charlie E. Jones; 
     “Oiless Rotary Scroll Air Compressor Antirotation Assembly”, U.S. patent application Ser. No. 09/584,711, filed on Jun. 1, 2000 by Michael V. Kazakis and Charlie E. Jones; 
     “Oiless Rotary Scroll Air Compressor Antirotation Lubrication Mechanism”, U.S. patent application Ser. No. 09/584,710, filed on Jun. 1, 2000 by Michael V. Kazakis and Charlie E. Jones; 
     “Oiless Rotary Scroll Air Compressor Axial Loading Support for Orbiting Member”, U.S. patent application Ser. No. 09/583,698, filed on Jun. 1, 2000 by Michael V. Kazakis and Charlie E. Jones; and 
     “Oiless Rotary Scroll Air Compressor Tip Seal Assembly”, U.S. patent application Ser. No. 09/584,324, filed on Jun. 1, 2000 by Michael V. Kazakis and Charlie E. Jones. 
     The subject matter disclosed in each of the above cross-referenced copending U.S. patent applications is hereby expressly incorporated by reference with the same effect as if fully set forth herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates, in general, to scroll compressors which are used to compress a fluid, for example, a gas such as a refrigerant for cooling purposes or ambient air in order to furnish a compressed air supply. 
     More particularly, the present invention relates to an improved air inlet valve assembly for use in such a rotary scroll compressor. 
     BACKGROUND OF THE INVENTION 
     So-called “scroll” compressors have achieved wider application recently, particularly in the fields of refrigeration and air conditioning, due to a number of advantages which they possess over reciprocating type compressors. Among these advantages are: low operating sound levels; reduction in “wear parts” such as compression valves, pistons, piston rings and cylinders (resulting in reduced maintenance); increased efficiency versus reciprocating compressor designs; and cooler operating temperatures. 
     While the number of wear parts in a scroll compressor may be reduced in comparison to a reciprocating type compressor, there are still a number of surfaces which move relative to one another and lubrication between these surfaces cannot be ignored. One design for a refrigerant scroll compressor utilizes an oil sump located in the lowermost portion of the compressor housing and an oil pump which draws oil from the sump upward to lubricate the moving parts of the compressor. The oil used as a lubricant in such a design is relatively free to mix with the air which is being compressed. Lubricating oil which becomes suspended in the refrigerant is, for the most part, separated therefrom by changing the direction of flow of the refrigerant and by impinging the refrigerant on surfaces located within the compressor. After it is separated, the oil is then drained back to the oil sump. 
     However, due to the gas having been relatively free to mix with the oil lubricant, the compressed gas exiting the scroll compressor may still have a relatively high degree of oil content. Such oil content may carry over to the compressed gas supply system and have deleterious effects such as reduced life of air driven mechanisms (e.g., air driven tools, brakes, etc.) which utilize the compressed gas supply as a power source. 
     OBJECTS OF THE INVENTION 
     One object of the present invention is the provision of a rotary scroll compressor which is “oiless” in the sense that the lubricant used to lubricate the various moving parts of the compressor is not intermingled with the gas being compressed. Thus, there is no contamination to the compressed gas due to the lubricant, and additional special provisions or designs need not be utilized for separating the lubricant from the compressed gas prior to using the compressed gas. 
     Another object of the present invention is the provision of a novel and inventive air inlet valve assembly for a rotary scroll compressor which serves to provide gas to be compressed (e.g., ambient air) to the suction region of the compressor while preventing a backward rotation of the orbiting scroll element after the power to the orbiting drive mechanism has been terminated. 
     Yet another object of the present invention is the provision of such an air inlet valve assembly which is inexpensive to manufacture and reliable in operation. 
     In addition to the objects and advantages of the present invention described above, various other objects and advantages of the invention will become more readily apparent to those persons skilled in the relevant art from the following more detailed description of the invention, particularly when such description is taken in conjunction with the attached drawing Figures and with the appended claims. 
     SUMMARY OF THE INVENTION 
     In one aspect, the invention generally features an air inlet valve assembly for a scroll compressor, the scroll compressor including a housing, a stationary scroll element mounted within the housing substantially stationary with respect to the housing, the stationary scroll element including a stationary spiral flange, an orbiting scroll element disposed within the housing, each of the stationary and orbiting scroll elements having a central axis, the orbiting scroll element including an orbiting spiral flange, the stationary and orbiting spiral flanges being intermeshed and nested with one another to define a compression pocket therebetween, an orbital drive mechanism for driving the central axis of the orbiting scroll element in an orbit about the central axis of the stationary scroll element while maintaining the orbiting scroll element substantially non-rotational with respect to the stationary scroll element, and an air inlet channel connecting to the compression pocket for supplying air to be compressed to the compression pocket, the air inlet valve assembly including a valve piston positioned within the air inlet channel, the valve piston having a first position substantially blocking the air inlet channel and a second position substantially unblocking the air inlet channel. 
     In another aspect, the invention generally features an improvement in a rotary scroll compressor of the type described, the improvement including an improved air inlet valve assembly having a valve piston positioned with an air intake channel connecting to the suction region of the compressor, the valve piston having a first position blocking the air intake channel and a second position unblocking the air intake channel. 
     In yet another aspect, the invention generally features a scroll compressor including an air inlet valve assembly for supplying air to be compressed, including a housing, a stationary scroll element mounted within the housing substantially stationary with respect to the housing, the stationary scroll element including a stationary spiral flange, an orbiting scroll element disposed within the housing, the orbiting scroll element including an orbiting spiral flange, each of the stationary and orbiting scroll elements having a central axis, the stationary and orbiting spiral flanges being intermeshed and nested with one another to define a compression pocket therebetween, an orbital drive mechanism for driving the central axis of the orbiting scroll element in an orbit about the central axis of the stationary scroll element while maintaining the orbiting scroll element substantially non-rotational with respect to the stationary scroll element and an air inlet channel provided through the housing, the air inlet channel connecting to the compression pocket and the air inlet valve assembly being for supplying air to be compressed to the compression pocket, the air inlet valve assembly including a valve piston positioned within the air inlet channel, the valve piston having a first position substantially blocking the air inlet channel and a second position substantially unblocking the air inlet channel. 
    
    
     The present invention will now be described by way of a particularly preferred embodiment, reference being made to the various Figures of the accompanying drawings, wherein: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is perspective view of an oiless rotary scroll compressor, constructed according to the present invention. 
     FIG. 2 is an exploded isometric view of the inventive oiless rotary scroll compressor. 
     FIG. 3 is a cross sectional elevational view of the inventive oiless rotary scroll compressor. 
     FIG. 4 is another cross sectional elevational view of the inventive oiless rotary scroll compressor, taken along a section rotated approximately 90° from the section of FIG.  3 . 
     FIG. 5 is a cross sectional plan view of the inventive oiless rotary scroll compressor. 
     FIG. 6 is an exploded isometric view of a crankshaft used in the inventive oiless rotary scroll compressor. 
     FIG. 7 is a cross sectional elevational view of the crankshaft of FIG.  6 . 
     FIG. 8 is an exploded isometric view of an anti-rotation assembly employed in the inventive oiless rotary scroll compressor. 
     FIG. 9 is a cross sectional view of the anti-rotation assembly of FIG.  8 . 
     FIG. 10 is a cross sectional elevational view of an angular contact bearing assembly which is preferably utilized in the anti-rotation assembly of FIGS. 8 and 9. 
     FIG. 11 is a cross sectional view through an orbiting spiral flange and a stationary spiral flange of the inventive oiless rotary scroll compressor, showing a novel tipseal assembly for providing a substantially airtight seal therebetween. 
     FIG. 12 is an isometric view of a tipseal element utilized in the tipseal assembly of FIG.  11 . 
     FIG. 13 is an enlarged view of a portion of the elevational cross section of FIG. 4, most particularly showing an air inlet valve assembly used to provide ambient air to be compressed to the inventive oiless rotary scroll compressor. 
     FIG. 14 is a cross sectional elevational view of an alternative embodiment of the air inlet valve assembly. 
     FIG. 15 is an exploded isometric view of the alternative air inlet assembly of FIG.  14 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Prior to proceeding to a much more detailed description of the present invention, it should be noted that identical components which have identical functions have been identified with identical reference numerals throughout the several views illustrated in the drawing Figures for the sake of clarity and understanding of the invention. 
     Referring initially to FIGS. 1 and 2, a scroll compressor constructed according to the present invention and generally designated by reference numeral  10  generally includes a bearing cap  12 , a crankshaft  14  positioned within the bearing cap  12  and a stationary scroll  16 . The stationary scroll  16  is bolted to the bearing cap  12  through a circular arrangement of bolts  18  with associated washers, lockwashers, etc. The stationary scroll  16  itself is provided with a series of radially extending fins  20  to improve the dissipation of heat therefrom. In the presently preferred embodiment, the radially extending fins  20  are preferably provided in the form of a separate bolt-on heat sink. The radially extending fins  20  could, however, be furnished integral with the stationary scroll  16 . A hood  22  substantially covers the fins  20  and is provided with a forced air intake  24  through which ambient air is preferably forced toward the stationary scroll  16  and fins  20  to aid in heat dissipation. This forced air escapes through a central aperture  26  and through openings  28  and  30  provided about the periphery of the hood  22 . The central aperture  26  also provides clearance for a compressed air discharge port  32  (i.e., a pressurized discharge region) located in the center of the stationary scroll  16 , while the peripheral opening  30  additionally provides clearance for an air inlet valve assembly  34  disposed on a peripheral portion of the stationary scroll  16 . 
     The crankshaft  14  is rotationally driven within the bearing cap  12  by a rotational power source of choice. For example, when the scroll compressor  10  is to be employed to supply compressed air for a pneumatic braking system of a diesel or electric rail transportation vehicle (e.g., a train or light rail vehicle), the crankshaft  14  will typically be rotationally driven by an electric motor. The crankshaft  14  in turn drives an orbiting scroll element  36  in an orbital motion within the bearing cap  12 . The orbiting scroll element  36  meshes with a stationary scroll element  37  (shown in FIGS. 3 and 4) which is preferably formed integrally with the stationary scroll  16  and is described more fully below. The mechanism by which the orbiting scroll element  36  is driven in such orbital fashion is more clearly shown in FIGS. 3,  6  and  7 , to which we now turn. 
     The crankshaft  14  includes an elongated shaft portion  38  having a central axis of rotation  40  about which the crankshaft  14  is rotationally driven by the power source of choice. An orbiting cylindrical bearing  42  is affixed to a first distal end of the crankshaft  14  adjacent the orbiting scroll element  36 . Preferably, this first distal end of the crankshaft adjacent the orbiting scroll element  36  is provided with a recessed cup portion  44  formed integrally thereon, and the orbiting cylindrical bearing  42  is disposed within the recessed cup portion  44 . The orbiting scroll element  36  also has a central axis  46  and is provided with a hub portion  48  which projects along this central axis  46  into the orbiting cylindrical bearing  42  to thereby rotationally engage the orbiting cylindrical bearing  42 . The orbiting cylindrical bearing  42  is positioned such that it is radially offset from the central axis of rotation of the crankshaft by a distance r, with the result that the orbiting cylindrical bearing  42 , the hub portion  48  and the orbiting scroll element  36  itself are all driven by the crankshaft  14  in an orbital motion having a radius of orbit equal to r about the central axis  40  of the crankshaft  14 . 
     In order to provide lubrication access to the orbiting cylindrical bearing  42 , the crankshaft  14  is provided with a lubricating channel  50  which extends from its second and opposite distal end to a point adjacent the orbiting cylindrical bearing  42 . Preferably, as shown, the lubricating channel  50  extends along the central axis  40  of the crankshaft member  14  to the recessed cup portion  44 . Provision of the lubricating channel  50  allows the orbiting cylindrical bearing  42  to be lubricated from a readily accessible single vantage point, namely, the second distal end of the crankshaft  14 , during maintenance. 
     The lubricating channel  50  also serves another function during assembly of the scroll compressor  10 . More particularly, during assembly, the hub portion  48  of the orbiting scroll element  36  enters the orbiting bearing  42 . During this step, the lubricating channel  50  serves as a vent, allowing any air that would be otherwise trapped to be vented. 
     The crankshaft  14  is additionally preferably furnished with a counterweight portion  52  that extends radially from the shaft portion  38  in a direction opposite to the radial offset r of the orbiting cylindrical bearing  42  from the central axis  40  of the crankshaft  14 . The crankshaft  14  is rotationally mounted within the bearing cap  12  through the provision of a main crankshaft bearing  54  and a rear crankshaft bearing  56 . The main crankshaft bearing  54  rotationally engages the shaft portion  38  at a point that is between the first distal end near the orbiting cylindrical bearing  42  and the second distal end of the crankshaft  14 , while the rear crankshaft bearing  56  rotationally engages the shaft portion  38  at a point that is between the main crankshaft bearing  54  and the second distal end of the crankshaft  14 . Both of the main and rear crankshaft bearings  54  and  56  may be, for example, of a caged roller bearing design or a caged ball bearing design. The orbiting cylindrical bearing  42  may be only of a caged roller bearing design. 
     The main crankshaft bearing  54  is preferably positioned within the bearing cap  12  by a main bearing sleeve  58  having a radially inwardly extending lip  60 . A rear bearing sleeve  62  similarly serves to position the rear crankshaft bearing  56  within the bearing cap  12 . As seen most clearly in FIGS. 6 and 7, a crankshaft locknut member  63  urges a crankshaft lockwasher member  64  into contact with a rear surface of the crankshaft rear bearing  56 . The rear bearing sleeve  62  is provided with an inwardly extending ledge  65 . A snap ring  67  (shown most clearly in FIGS. 4 and 7) snaps into a groove encircling the exterior face of the rear crankshaft bearing  56 . The snap ring  67  limits axial movement of the crankshaft  14  in an upward direction (as seen in FIG.  4 ), thereby locking the crankshaft axially within the bearing cap  12 . 
     As shown in FIGS. 3 and 7, the recessed cup portion  44  is provided with an annular ledge  66  spaced away from the bottom of the recessed cup portion  44 . The orbiting cylindrical bearing  42  rests on this annular ledge  66  to thus create a lubrication reservoir  68  beneath the orbiting cylindrical bearing  42 , the lubrication reservoir  68  being connected to the lubrication channel  50 . An orbiting seal  43  overlays the orbiting cylindrical bearing  42  within the recessed cup portion  44 . 
     The orbiting scroll element  36  includes an orbiting base member  70  and an orbiting spiral flange  72  projecting outward therefrom. In order to provide the stationary scroll element  37  referred to above, the stationary scroll  16  is in turn provided with a preferably integrally formed stationary spiral flange  74  which projects outward from the stationary scroll  16  and has a common central axis  40  with the crankshaft  14 . As seen most clearly in FIGS. 3 and 5, the stationary and orbiting spiral flanges  74  and  72 , respectively, are intermeshed and nested with one another. For those not familiar with the manner in which compression is achieved in a scroll-type compressor, the compression mechanics may be difficult to visualize. However, for those of ordinary skill in the scroll-type compressor arts, the compression mechanics are well understood. In brief, the stationary scroll flange  74 , being affixed to or an integrally formed portion of the stationary scroll  16 , is maintained stationary. The orbiting scroll flange  72  executes an orbit of radius r with respect to the stationary scroll flange  74  and, during such orbiting motion, is maintained substantially non-rotational with respect to the stationary scroll flange  74 . In other words, one may picture the stationary scroll flange  74  as having a stationary central axis z(stationary)  40 , as well as remaining orthogonal coordinates x(stationary) and y(stationary) lying within the plane of the stationary spiral flange  74 . One may also picture the orbiting spiral flange  72  as having an orbiting central axis z(orbiting)  46 , as well as remaining orthogonal coordinates x(orbiting) and y(orbiting) lying within the plane of the orbiting spiral flange  72 . In such case the orbiting motion which causes compression can be best described as an orbiting of the z(orbiting) central axis  46  about the z(stationary) central axis  40 , while the remaining x and y axes of the stationary and orbiting spiral flanges remain in a parallel relationship to one another. In other words, the orbiting motion is accomplished with substantially no relative rotational motion occurring between the orbiting spiral flange  72  and the stationary spiral flange  74 . 
     During such described motion, a compression pocket will be formed during each revolution of the orbiting spiral flange  72 . The compression pocket so formed will spiral toward the central area of the intermeshed stationary and orbiting spiral flanges  74  and  72 , respectively, advancing and undergoing a compression step during each orbit. The number of revolutions required for a compression pocket so formed to reach a compressed air output  76  (which is located generally in the vicinity of the stationary central axis  40 ) depends on how many revolutions each of the stationary and orbiting spiral flanges  74  and  72 , respectively, are provided with. In the present embodiment, each of the stationary and orbiting spiral flanges  74  and  72 , respectively, is provided with somewhat over three revolutions. Preferably, each of the stationary and orbiting spiral flanges  74  and  72 , respectively, extends over an arc of about 1350°, i.e., about 3¾ revolutions. 
     Referring now primarily to FIG. 5, the orbiting spiral flange  72  has a radially outward terminus portion  78 . As the radially outward terminus portion  78  of the orbiting spiral flange  72  separates from the corresponding portion of the stationary spiral flange  74  during each non-rotational orbit, a progressively wider gap is formed into which low pressure air is introduced from a generally peripherally located suction region  80 . As the orbiting spiral flange non-rotationally orbits further, this gap is eventually closed by the contact of the terminus portion  78  with the corresponding portion of the stationary spiral flange  74 . The described action forms a compression pocket which spirals inward toward the centrally located compressed air output  76  during successive orbits of the orbiting spiral flange  72 . Two successive compression pockets are generally designated as  82  and  84  in FIG. 5, with the more radially inward compression pocket  84  being more highly compressed than the more radially outward compression pocket  82 . 
     In order to prevent any relative rotational movement between the stationary and orbiting spiral flanges  74  and  72  while simultaneously permitting the orbiting of the scroll element  72  through the orbit of radius r under the influence of the orbital drive mechanism described above, the scroll compressor  10  is additionally provided with an anti-rotation device  90  most clearly seen in FIGS. 3,  8  and  9 , to which we now turn. 
     The bearing cap  12  is provided with a bearing face portion  86  (seen in FIGS.  2 , 3 , 4  and  9 ) which is formed as a semi-annular ledge projecting radially inward from the interior surface of the bearing cap  12 . The bearing face portion  86  is provided with a cutout  88  (seen in FIG. 2) in order to provide clearance for the counterweight portion  52  of the crankshaft  14  during assembly/disassembly. Three anti-rotation assembly assemblies  90  are arranged equidistant from and preferably equally angularly spaced around the common central axis  40  of the stationary scroll element  37  and the crankshaft  14 . Thus, the three anti-rotation assembly assemblies  90  are preferably spaced at angular intervals of 120°. In the presently preferred embodiment, each of the anti-rotation assembly assemblies  90  is radially spaced outward from the common central axis  40  of the crankshaft  14  and the stationary scroll element  37  at a distance R which is preferably substantially equal to about 5 inches. 
     Each anti-rotation assembly  90  includes a first rotational bearing  92  which is mounted fixedly and stationary with respect to the stationary scroll element  37 , preferably in a the bearing face portion  86  (as shown in FIGS. 3 and 9) and a second rotational bearing  94  which is mounted fixedly on the orbiting scroll element  36 . Preferably, each first rotational bearing  92  is disposed in a first cavity  96  provided in the bearing face portion  86 , while each second rotational bearing  94  resides in a corresponding second cavity  98  provided in the orbiting scroll element  36 . Each anti-rotation assembly  90  further includes an offset crank member  100  having a first shaft portion  102  which engages the first rotational bearing  92  and a second conically tapered shaft portion  104  which engages a similarly conically tapered cavity  110  provided in a bushing member  106  which rotationally engages the second rotational bearing  94 . The first and second shaft portions  102  and  104 , respectively, are aligned substantially in parallel to one another and are separated by a radially offset distance r which is substantially equal to the radial offset r between the central axis  46  of the orbiting scroll element  36  and the common central axis  40  of the stationary scroll element  37  and the crankshaft  14 , the distance r also being the radius of orbit of the orbiting scroll element  36 . 
     The present inventors have discovered that a particularly effective method for providing the engagement between the second shaft portion  104  of the offset crank member  100  and the second rotational bearing  94  is through the provision of the bushing member  106  which is itself non-rotationally engaged with the second shaft portion  104  but is rotationally engaged with the second rotational bearing  94 . To this end, the second shaft portion  104  is provided with a conically tapered portion  108  which non-rotationally connects via a friction push fit with the similarly tapered cavity  110  provided in the bushing member  106 . The non-tapered exterior periphery of the bushing  106  then rotationally mates with the second rotational bearing  94 . 
     During operation of the scroll compressor  10 , the pressure that is built up (e.g., in the spiraling compression pockets  82  and  84 ) exerts an axial force, that is a force acting parallel to the central axes  40  and  46  which tends to separate the stationary and orbiting spiral elements  37  and  36 , respectively, from one another. From the viewpoint of merely providing for a rotational motion between the first shaft portion  102  and the first rotational bearing  92  and also between the bushing member  106  and the second rotational bearing  94 , it is sufficient to furnish the first and second rotational bearings  92  and  94 , respectively, in the form of conventional ball bearing assemblies or conventional roller bearing assemblies. Back pressure could then, for example, be utilized to balance or compensate for the above-noted axial forces which tend to separate the stationary and orbiting spiral elements  37  and  36 , respectively. However, the present inventors have discovered that by utilizing a particular type of bearing for the first and second rotational bearings  92  and  94 , respectively, the above-noted separating axial forces may be neutralized directly, thus eliminating the requirement of utilizing back pressure. In this regard, the rotational bearing components  92  and  94 , respectively, are each preferably furnished in the form of angular contact bearing assemblies  112 , an example of which is shown most particularly in FIG.  10 . FIG. 10 shows the second rotational bearing  94  being provided as an angular contact bearing assembly  112  and the positioning of the second rotational bearing  94  relative to the central axes  40  and  46  during one extreme of the rotational orbit. It will be understood that the first rotational bearing  92  may be likewise provided in the form of a similar angular contact bearing assembly  112 . Preferably, both of the first and second rotational bearing components  92  and  94 , respectively, are provided in the form of an angular contact bearing assembly  112 . 
     As seen in FIG. 10, the angular contact bearing assemblies  112  which are preferably employed for the first and second rotational bearing components  92  and  94 , respectively, include at least one bearing surface  114  and/or  116  which projects a non-zero component parallel to the direction of the central axis  40  of the stationary scroll element  37  and parallel to the direction of the central axis  46  of the orbiting scroll element  36 , both central axes  40  and  46  being parallel to one another. Due to the fact that the bearing surfaces  114  and/or  116  have a non-zero component projecting in a direction parallel to the central axes  40  and  46 , the angular contact bearing assemblies  112  are able to resist the above-noted axial forces generated during compression which tend to exert a separating force between the stationary and orbiting scroll elements  37  and  36 , respectively. Preferably, the angular contact bearing assemblies  112  employed are angular contact ball bearing assemblies and are of a single row configuration. Such angular contact ball bearing assemblies are available commercially and are well known to those of ordinary skill in the mechanical arts. Such angular contact ball bearing assemblies typically include two such bearing surfaces  114  and  116  which are angled so as to resist angular forces (i.e., having non-zero components in two orthogonal directions) applied thereto. 
     While it is possible to provide the rotational bearing components  92  and  94  in the form of sealed pre-lubricated bearing assemblies, in its presently preferred embodiment, the scroll compressor  10  includes a lubrication apparatus  118  for allowing the rotational bearing components  92  and  94  to be periodically lubricated. Provision of the lubrication apparatus  118  allows for a longer life of the first and second rotational bearing components  92  and  94 , respectively. Utilizing sealed pre-lubricated bearings could necessitate a costly disassembly procedure for replacement of the bearings near the end of their rated life. The provision of the lubrication apparatus  118  is made possible by a further unique construction of the anti-rotation assembly assemblies  90 , wherein each of the first rotational bearing components  92  is fixedly mounted within the bearing cap  12  and wherein a lubrication channel portion is provided which interconnects the respective first and second rotational bearing components  92  and  94 , respectively. 
     Referring most particularly to FIG. 3, a lubrication port  120  is disposed on the exterior surface of the bearing cap  12  adjacent each of the anti-rotation assembly assemblies  90 . A lubrication channel  122  extends from each of the lubrication ports  120  to at least a point adjacent the first rotational bearing  92  of the associated anti-rotation assembly  90 . As is shown most particularly in FIG. 9, a channel portion  124  passing through the offset crank member  100  extends the lubrication channel  122  so that it ultimately extends to another point adjacent the second rotational bearing  94 . A lubricating agent (e.g., grease) introduced into the lubrication channel  122  through the lubrication port  120  lubricates the first rotational bearing  92  via the first cavity  96  provided in the bearing face portion  86  in which the first rotational bearing  92  is mounted. Additionally, the lubricating agent is conducted through the channel portion  124  in the offset crank member  100  to the second cavity  98  provided in the orbiting scroll element  36 , thereby lubricating the second rotational bearing  94 . 
     As noted above, the orbiting spiral flange  72  and the stationary spiral flange  74  are nested and intermeshed with one another to form the spiraling compression pockets illustrated by the compression pockets  82  and  84  shown in FIG.  5 . In order to provide a substantially airtight seal for these spiraling compression pockets (e.g.,  82  and  84 ) the present scroll compressor  10  employs a unique “tipseal” assembly  126 , generally illustrated in FIG.  3  and most particularly shown in FIGS. 11 and 12, to which we now turn. 
     The orbiting spiral flange  72  projecting outward from the orbiting base member  70  of the orbiting scroll element  36  terminates in an end surface  128  which is positioned immediately adjacent to and opposes the stationary scroll  16 . Similarly, the stationary spiral flange  74  projecting outward from the stationary scroll  16  terminates in an end surface  130  which is positioned immediately adjacent to and opposes the orbiting base member  70 . Each of the end surfaces  128  and  130  are provided with an inwardly extending groove  132  and  134 , respectively. Preferably, each of the grooves  132  and  134  extends substantially over the entire extent of the associated end surface  128  and  130 , respectively. A compressible element  136  is disposed within the groove  132 , and another compressible element  138  is similarly disposed within groove  134 . A first tipseal element  140  overlays compressible element  136 , while a second tipseal element  142  overlays compressible element  138 . 
     The depths of the grooves  132  and  134 , the heights of the compressible elements  136  and  138  and the heights of the tipseal elements  140  and  142  are all selectively chosen such that, with these components in their assembled configuration and with the compressible elements  136  and  138  in a substantially uncompressed state, each respective tipseal element  140  and  142  extends beyond the respective end surface  128  and  130  by a measurement ranging between about 0.018 inch and 0.022 inch. Stated another way, the combined height of the compressible element  136  and the tipseal element  140  exceeds the depth of the groove  132  by about 0.018 inch to about 0.022 inch when the compressible element  136  is in a substantially compressed state. Similarly, the combined height of the compressible element  138  and the tipseal element  142  exceeds the depth of the groove  134  by about 0.018 inch to about 0.022 inch when the compressible element  138  is in a substantially compressed state. 
     When the scroll compressor is in its assembled state (for example, as shown in FIG.  3 ), the compressible elements  136  and  138  will become somewhat compressed such that they exert biasing forces on the respective tipseal elements  140  and  142  urging them into contact with the respective opposing surfaces of stationary scroll  16  and orbiting base member  70  to thereby form substantially airtight seals for the spiraling compression pockets (e.g.,  82  and  84 ) formed between the nested and intermeshed stationary scroll element  37  and orbiting scroll element  36 . 
     The present inventors have achieved good performance by providing the compressible elements  136  and  138  in the form of an elongated O-ring made of an elastomeric material, most preferably a silicone rubber material, and even more preferably a high temperature resistant O-ring material. Similarly, good performance has been achieved by furnishing the tipseal elements  140  and  142  in the form of a non-metallic substance, preferably a PTFE based product, and most preferably a fluorosint material. 
     The air inlet valve assembly  34  discussed briefly above in connection with FIGS. 1 and 2 is more particularly illustrated in FIGS.  4  and  13 - 15 , to which we now turn. 
     The air inlet valve assembly  34  is provided in order to conduct ambient air to the suction region  80  (shown in FIGS. 5 and 13) which is located generally peripherally around the orbiting and stationary spiral flanges  72  and  74 , respectively, and to also prevent any backward rotation of the orbiting scroll element  36  upon shut down of the power source which drives the crankshaft  14 . To this end, an air inlet channel  144  connects the ambient environment located outside of the bearing cap  12  to the suction region  80  located within the bearing cap  12 . As shown in FIG. 4, the air inlet channel  144  preferably passes through the stationary scroll  16 . In the configuration of FIG. 4, a portion of the air inlet channel  144  is formed by an air inlet port  146  formed in the stationary scroll  16 . The air inlet valve assembly  34  includes a valve piston  148  which is positioned within the air inlet channel  144 . The valve piston  148  is moveable between a first position (shown in FIGS. 4,  13  and  14 ) wherein the valve piston  148  substantially blocks any flow through the air inlet channel  144  and a second position wherein the valve piston  148  substantially unblocks flow through the air inlet channel  144 . 
     The valve piston  148  is biased toward the first blocking position by a biasing member  150 . More particularly, the air inlet valve assembly  34  further includes a valve seat  152  which is mounted stationary with respect to the stationary scroll  16 , and the biasing member  150  urges the valve piston  148  into contact with the valve seat  152  thereby preventing flow past the valve piston  148  and substantially blocking the air intake channel  144 . The valve seat  152  is disposed on the opposite side of the valve piston  148  from the suction region  80 , and therefore, the force exerted by the biasing member  150  is in a direction substantially away from the suction region  80 . 
     In the embodiment shown in FIGS. 2,  4  and  13 , a valve housing  154  is provided which connects to the stationary scroll  16  via bolts  156 . The valve piston  148  is disposed within a valve cavity  158  that is formed within the valve housing  154 , and the valve seat  152  is provided as a surface formed within the valve cavity  158  enclosed by the valve housing  154 . A valve stem  160  is connected to and extends from the valve housing  154  in the direction of the suction region  80 . The valve piston  148  surrounds the valve stem  160  and is able to reciprocate in a sliding fashion thereon. A first stop surface  162  is formed on the valve piston  148 . A second stop surface  164  is formed on the valve stem  160  and is disposed between the first stop surface  162  formed on the valve piston  148  and the suction region  80 . The biasing member  150  is preferably provided in the form of a coil spring  166  which encircles the valve stem  160  between the first stop surface  162  and the second stop surface  164 . The valve piston  148  is able to slide along the valve stem  160  in the direction of the suction region  80  to admit ambient air to be compressed against the biasing force exerted by the coil spring  166 . Movement of the valve piston  148  in the direction of the suction region  80  is limited by contact of the first stop surface  162  provided on the valve piston  148  with the second stop surface  164  formed on the valve stem  160 . 
     In the embodiment of the air inlet valve assembly  34  shown in FIGS. 2,  4  and  13 , it is possible that vibration characteristics could be introduced by the presence of the biasing element  150  (e.g., the coil spring  166 ). In such cases, the present inventors have discovered that the biasing element  150  (e.g., coil spring  166 ) and its associated supporting structures may be eliminated from the design without introducing any serious compromise in function. 
     FIGS. 14 and 15 illustrate an alternative embodiment of the air inlet valve assembly  34  which functions in substantially the same manner as described above but which is provided with a somewhat differently configured air intake valve body  168  having an air intake conduit  170  extending therefrom. 
     While the present invention has been described by way of a detailed description of a particularly preferred embodiment or embodiments, it will be apparent to those of ordinary skill in the art that various substitutions of equivalents may be affected without departing from the spirit or scope of the invention as set forth in the appended claims.