Patent Publication Number: US-6341948-B2

Title: Internal oil filter element for refrigeration compressor

Description:
This application is a divisional of Ser. No. 09/204,868 filed on Dec. 3, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a refrigeration compressor having an oil filter. In particular, the present invention is directed to the placement of the oil filter within the body of the compressor. 
     A refrigeration compressor is an integral part of a refrigeration unit, along with an evaporator, expansion valve, and condenser. A compressor compresses the refrigerant, thus raising its temperature. This compressed refrigerant gas then enters the condenser and is condensed into liquid form by contacting it with another cooler medium, such as ambient air, ground water, or water from a cooling tower loop. After the heat is removed from the refrigerant in the condenser, the condensed refrigerant liquid goes to an expansion valve. The expansion valve allows a limited quantity of liquid refrigerant to enter the evaporator, while maintaining the pressure difference between the condenser (at higher pressure) and the evaporator (at lower pressure). The liquid refrigerant entering the evaporator evaporates after contacting a heat load, such as the refrigerator interior or ventilation air that is to be cooled, thus absorbing heat from the heat load. The refrigerant vapor leaves the evaporator and returns to the compressor to repeat the cycle. 
     A refrigeration compressor commonly has a cast metal housing and a need for lubrication of the moving parts, such as the gears and bearings. A refrigeration compressor contains an oil sump where lubricating oil collects and a lubrication system to direct oil from the sump to each lubrication point. The oil lubrication system has an oil filter for removing particulate matter from lubrication oil. 
     The oil filter associated with a refrigeration compressor has been provided in a separate pressure vessel attached onto the outside of the compressor, or even contained in a separate pressure vessel unattached to the compressor body. 
     Having a separate pressure vessel increases the potential for oil leaks. In addition, an oil filter attached to the housing of a compressor is not easily replaced. In many refrigeration compressors in the prior art it is quite difficult to replace the oil filter without losing the charge of refrigerant. Another problem with prior art refrigeration compressors and their separate oil filters is that the oil filter element itself gets contaminated quite easily, and this greatly reduces its filtering efficiency. External oil filters also make it more difficult for clean, filtered oil to reach the lubrication points, since the oil has to travel farther (and thus pick up more impurities) to get to its targets. In addition, an oil filter vessel projecting from the compressor is exposed and subject to injury, particularly when the compressor is being shipped and installed. 
     U.S. Pat. No. 5,159,820 discloses an oil separator integrally mounted on a compressor. In this patent, elements that separate the refrigerant from the oil and then filter the oil are attached to the compressor casting and operatively connected to the compressor. This reference, however, does not disclose an oil filter located inside of the compressor casting. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the invention is to provide an oil filtration system having fewer leak points. 
     A further object of the invention is to enable the filter element to be replaced while the compressor is charged with refrigerant. 
     Another object of the invention is to allow cleaner oil to reach the lubrication points in the compressor. 
     Still another object of the invention is to provide an oil filter which does not project outward from the compressor. 
     To achieve at least one of the objects at least in part, and in accordance with the purpose of the invention, as embodied and broadly described herein, the refrigeration compressor of the present invention includes a cast member and a cavity formed in that cast member. The cavity is divided into an inlet cavity and outlet cavity by a filter element. The compressor also includes an inlet port for directing unfiltered oil into the inlet cavity and an outlet port for directing clean oil away from the outlet cavity. 
     Two advantages of this invention are that the possibility of oil leaks is reduced and cleaner oil reaches the lubrication points in the compressor. A further advantage of this internal oil filter is to allow easy replacement of the inexpensive filter element (as opposed to the whole oil filter vessel) while the compressor is charged with refrigerant. A further advantage of this invention is to minimize the possibility that the filter vessel will be damaged during shipping or installation of the compressor. 
     Additional objects and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
     The present invention provides a refrigeration compressor. The compressor comprises a cast member with a cavity formed in the cast member. An oil filter element divides the cavity into an inlet cavity and an outlet cavity. The cavity includes an inlet port for directing oil to be filtered into the inlet cavity, and an outlet port for directing filtered oil out of the outlet cavity. 
     The present invention also provides a gear driven refrigerant compressor. The compressor comprises: a housing; a low speed drive shaft with an integrally mounted bull gear; and a pinion drive shaft with a pinion drive gear engaging the bull gear, all located in an upper region of the housing. The compressor also includes an oil sump located in a lower region of the housing; and an oil filter cavity formed in an intermediate region of the housing between the upper region and the lower region, the cavity containing an oil filter. 
     The present invention further provides that the oil filter include at least one end cap having eared elements where the eared elements act as a spacer between the cavity and the oil filter. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIG. 1 is a side elevation of the invention, cut away and drawn partially in section to show the interior features. 
     FIG. 2 is a side elevation view showing the opposite side of the refrigeration compressor compared to FIG. 1, and specifically showing the oil filter cavity. 
     FIG. 3 is a fragmentary cross-section, taken along line  3 — 3  in FIG. 2, depicting the inside of the oil filter cavity. 
     FIG. 4 is an isolated side elevation of an end cap  83  taken along line  4 — 4  of FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the embodiment of the invention illustrated in the accompanying drawings. The same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     While the invention will be described in connection with one or more embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications, and equivalents as may be included within the spirit and scope of the appended claims. 
     FIG. 1 depicts a gear-driven refrigeration compressor  12  that includes impellers  16  and  20  carried on a pinion drive shaft  18  and a motor  22  to drive the pinion drive shaft  18 . The compressor  12  has a refrigerant gas inlet  51  and internal passages  30  directing refrigerant gas into and through the impellers  16  and  20 . 
     The motor  22  drives a low-speed output shaft  34 . A bull gear  38  is attached to the low speed shaft  34 , and drives the pinion gear  46  which is integral with the pinion drive shaft  18 . A direct drive compressor (not illustrated) would have the motor  22  directly attached to the pinion drive shaft  18  that drives the impellers  16  and  20 . 
     A conduit  50  from the evaporator (not shown) feeds refrigerant vapor to the gas inlet  51 . The internal passages  30  include circular diffuser passages  31   a ,  31   b  and a gas collecting space known as a volute  33  at the perimeter of the compressor  12 . In operation, hot refrigerant vapor enters the gas inlet  51  from the piping conduit  50  and flows to the first impeller  16 . Once the gas is inside the rotating first impeller  16 , this rotation accelerates the gas radially outward. In a multi-stage compressor  12 , the compressed gas is guided by the internal passage  30  from the first impeller  16  into the second impeller  20  where the gas is again radially accelerated. 
     The gas exits the second impeller  20  into a circular diffuser passage  31   b  and then into the volute  33  at the perimeter of the compressor  12 . As the gas flows to the volute  33 , the volume of the passages available for gas flow increases, thereby reducing the velocity of the gas flow. The pressure of the gas is increased as it travels through and around the impellers  16 ,  20 . Eventually, the gas has reached the desired compression ratio and is directed out of the compressor  12  to a condenser (not shown). 
     A cast member  56  defines a housing for the refrigerant compressor  12 . An oil filter cavity  52  is shown cast in the cast member  56 , preferably between the oil sump  58  and the compressor lubrication points, these lubrication points including the gears  42 ,  46  and the various bearings for the shafts  18 ,  34 . 
     FIG. 2 is an elevation of the opposite side of the refrigeration compressor  12  showing the oil filter cavity  52  (also visible in FIG. 3) cast into the cast member  56 , and an oil sump  58 . 
     FIG. 3 shows more details of the filter cavity  52  in the cast member  56 . The filter cavity  52  is a recess in the outer surface  54  of the cast member  56  having a generally cylindrical wall  55 . The generally cylindrical wall  55  can be non-cylindrical without departing from the present invention. 
     The filter cavity  52  can be formed by providing a core in the mold in which the cast member  56  is formed. Alternatively, the cavity  52  can be machined or otherwise formed. The filter cavity  52  has an inlet port  61  communicating from the outer surface  54  of the casting  56  to the filter cavity  52 . The inlet port  61  is provided with a socket recess  62  to receive a suitable conduit  72  communicating with the oil sump  58  and an oil pump (not shown). The filter cavity  52  also includes steps  84  and  91 . 
     A removable filter cover  68  having a bearing surface  69  is fastened to the outer surface  54  of the casting  56  to cover the filter cavity  52 . Screws or other fasteners (not shown) providing access to the filter cavity  52  are suitable. The filter cover  68  has an outlet port  60  communicating with filtered oil in an outlet cavity  74  and having a socket recess  71  to receive a suitable conduit  59  communicating with one or more lubrication points such as the bull gear  38  shown in FIG.  2 . 
     An oil filter element  73  is located within the filter cavity  52 . The filter element  73  is a tubular member made of a suitable filtering material. The filter cavity  52  is divided by the filter element  73  into an inlet cavity  76  communicating with the inlet port  61  and the outlet cavity  74  communicating with the outlet port  60 . The filter element  73  has an outer perforated metal jacket  75 , an inner perforated metal jacket  79  defining a hollow interior, and first and second ends  80  and  81 . The filter element  73  includes end caps  82  and  83 . The end cap  82  is closed, thus allowing no oil to bypass the second end  81 . As shown in FIG. 4, the end cap  83  has a hole  85  in it to allow filtered oil to escape the filter element  73  through the outlet port  60 . The end caps  82  and  83  have ears  87  and  88 , respectively, as shown in FIG.  4 . 
     As shown in FIG. 3, an integral plate  89  is part of the first end  80  of the filter element  73 . The ears  87  and  88  bear against the sides of the filter cavity  52  thus entering the filter element  73 . An o-ring or other suitable sealing element  90  is provided to seal between the inlet cavity  76  and the outlet cavity  74 . The integral plate  89  bears against and compresses the o-ring  90  against the step  91  in the filter cavity  52 . The integral plate  89 , and thus the entire filter element  73 , is held in pace between the filter cover  68  and the o-ring or other sealing element  90 . The filter cover  68  bears against an additional o-ring or other suitable sealing element  92  between the filter cover  68  and the surface  54  to seal the filter cavity  52  with respect to ambient air. Isolation valves  93  and  94  are provided to prevent or allow flow through the inlet port  61  and outlet port  60 , respectively. 
     As shown in FIG. 3, during normal operation the unfiltered oil enters the inlet cavity  76  through the inlet port  61 . The entering oil circulates in the inlet cavity  76  around the outside of the filter element  73 . As the oil passes through the filter element  73 , the oil is filtered and then passes to the outlet cavity  74 , then through the outlet port  60 . The sealing element  90  prevents oil from bypassing the filter element  73  from the inlet cavity  76  directly to the outlet cavity  74 . During normal operation, the isolation valves  93  and  94  are opened to allow flow through the inlet port  61  and outlet port  60 , respectively. 
     When the filter element  73  is to be inspected, serviced, replaced or accessed for some other reason, the isolation valves  93  and  94  are closed. This isolates the filter cavity  52  from the rest of the lubrication system. The filter cover  68  can then be removed without losing oil or pressure in other parts of the lubrication or refrigerant system, and access to the filter element  73  is provided. If the element  73  is to be replaced, for example, it can readily be slid out of the cavity  52  and replaced by another filter element such as  73 . After access to the filter cavity  52  is no longer necessary, the filter cover  68  is fastened in place and the isolation valves  93  and  94  are re-opened to restore flow. Make-up oil can be added conventionally to replace any oil lost when the filter element  73  is removed. 
     Two advantages of this invention are that the possibility of oil leaks is reduced and cleaner oil reaches the lubrication points in the compressor. A further advantage of this internal oil filter is to allow easy replacement of the inexpensive filter element (as opposed to the whole oil filter vessel) while the compressor is charged with refrigerant. A further advantage of this invention is to minimize the possibility that the filter vessel will be damaged during shipping or installation of the compressor. 
     The invention has been shown and described in preferred form only, and by way of example, and many variations may be made in the invention that will still be within the spirit of the invention. It is understood, therefore, that the invention is not limited to any specific embodiment except insofar as such limitations are included in the appended claims. 
     Other embodiments of the invention will be obvious to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.