Patent Publication Number: US-6698232-B1

Title: Oil leak diversion and collection system for mechanical shaft seals

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system for controlling oil seepage from a compressor. More particularly, the present invention concerns a system for diverting and collecting excess oil originating in the area of the shaft seal of the crankshaft of a reciprocating compressor. 
     2. Background Art 
     Refrigeration systems, such as the type used in transport refrigeration equipment, include, in the simplest form, a compressor, a condenser, an expansion device and an evaporator serially interconnected to form a closed refrigeration circulation path. Typically, such systems use a reciprocating type compressor that is lubricated by a lubricating oil which mixes with the refrigerant being compressed therein. 
     A typical reciprocating compressor includes a piston reciprocating within a cylinder for mechanically compressing gaseous refrigerant. Appropriate manifolds and valves are provided to allow gas to be drawn into the cylinder during the down stroke of the piston and to be compressed during the up stroke. 
     Oil is used in such compressors to lubricate the various parts and interfaces there between. To maintain refrigerant pressure within the compressor, mechanical shaft seals are used that deploy an oil film to seal against the leakage of pressurized gas and to lubricate the faces of the seal during operation. For example, such seals are used on the crankshaft of the compressor such as in the vicinity of the gland plate. Oil leakage across the seal faces is a common problem with any mechanical shaft seal. If such oil is allowed to leak unabated, external oil leakage through the crankcase can result. Typically such leakage is more visually unpleasing and alarming rather than detrimental to compressor function; however, such leakage often leads to unnecessary component replacement of the mechanical shaft seal components. 
     Accordingly, devices have been deployed to divert excess oil from the crankshaft seal area to hide external leakages. One such device is an external masking device used on an open-drive compressor known as the Bock FKX40/465. The device allows oil to leak to an external pocket, which is open to the atmosphere, on the outside of the gland plate and then utilizes an absorbent material to capture the excess oil over flowing therefrom. The absorbent material is encapsulated by a band of spring steel that is wrapped around the outside diameter of the material which is in turn wrapped around the gland plate housing in proximity to the external pocket. 
     While effective, these types of designs use an oil soaked external absorbent band which attracts dirt and can soil its surroundings, adding to the soiling of the external surfaces of the compressor. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to reduce oil leakage in a device using shaft seals. 
     It is a further object of the present invention to provide an improved mechanism for diverting excess oil away from a shaft seal. 
     It is another object of the present invention to provide an improved mechanism for collecting excess oil after its diversion from a shaft seal. 
     It is another object of the present invention to provide a means for absorbing excess oil from the vicinity of a shaft seal. 
     It is still another object of the present invention to provide a means for providing external notice of excess oil absorbed from the vicinity of a mechanical shaft seal 
     These and other objects of the present invention are achieved according with the compressor oil diversion and collection system of the present invention, for use in a compressor having a housing, a crankshaft having shaft seals, refrigerant and a compression device for compressing the refrigerant. The system includes a shaft sealing mechanism that uses a lubricant for preventing compressor refrigerant from leaking out of the compressor housing and has a space where the lubricant collects. A diversion mechanism is deployed for directing excess amounts of the lubricant from the space to a receiver for receiving the excess amounts of said lubricant from the diversion mechanism. The receiver may be in the form of an internal cavity which includes a removable cartridge located in the cavity to collect the excess amount of lubricant, an external collection reservoir or an external drainage tube. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a reciprocating compressor incorporating the device of the present invention; 
     FIG. 2 is an enlarged view of the crankshaft seal area of FIG. 1; 
     FIG. 3 is an exploded end view of the compressor shown in FIG. 1, with the absorbent cartridge shown being installed; 
     FIG. 4 is a further blown up view of the view shown in FIG. 2; 
     FIG. 5 is an enlarged cut-away view of FIG. 3, showing the oil flow passages; 
     FIG. 6 is an enlarged view of the absorbent cartridge shown in FIG.  3 . 
     FIG. 7 is an end view of the compressor shown in FIG. 1, showing an external reservoir as an alternative embodiment of the present invention; 
     FIG. 8, is the same view as FIG. 7 without the external reservoir attached; and 
     FIG. 9 is a view similar to FIG. 7, showing an alternative design using an overflow tube. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention as described herein will refer to a reciprocating compressor for use with an air conditioning or refrigeration system. Although this compressor is shown in a configuration and described relative to incorporation with a refrigeration circuit within an air conditioning system or a refrigeration system it is to be understood that this method of oil collection and diversion is equally applicable to other types of compressors, pumps and other applications. 
     Referring now to FIG. 1, shown is a compressor  10  including shell  12 . Working pistons  14  are mounted for reciprocating movement within cylinders  16 . Each piston is connected to crankshaft  18  via a connecting rod  20 . Connecting rod  20  is secured around offset portion  22  of crankshaft  18 . Crankshaft  18  includes counterbalance  24  for balancing the rotational irregularities in the crankshaft. The crankshaft is mounted and rotates within sleeve  28  and extends through shaft seal cavity  26  of housing  12 . 
     Referring to FIG. 2 and 4, the crankshaft seal mechanism  31  is shown in greater detail at the point where the housing  12  is exited by the crankshaft. The crankshaft  18  passes through the spring assembly  45 , shaft seal faces  29  and  33 , gland plate  32  and lip seal  38 . The face seal  33  is substantially cylindrical in shape and includes an O-ring  36 , which holds it stationary within inner diameter A of the gland plate  32 . The lip seal  38 , located in gland plate adjacent to diameter A, in smaller diameter B, has the function of preventing dirt from entering the shaft seal cavity. An inner disc-shaped space  40  is located between face seal  33  and lip seal  38 . As shown in FIG. 3, a gland plate gasket  35  is used to prevent seepage between the housing and the gland plate. 
     The crankshaft seal mechanism further includes a cylindrical body  44  formed from a resilient material, using oil between it and the crankshaft to act as a refrigerant seal. A spring  45  wrapped around the exterior of the body  44  and resting against the crankshaft seal thrust face provides axial loading between the two shaft seal faces  29  and  33 . The two faces are loaded such that, with the use of oil, they will act as a refrigerant seal. In the prior art, where oil passing across the two shaft seal faces is not removed or redirected, it will pass through crankshaft to the lip seal interface that is located as shown in FIG. 3, leading to leakage and soiling of the external surfaces of the compressor. This external leakage and soiling often leads to incorrect conclusions that a serious mechanical problem exists with the compressor. 
     The invention as provided herein operates to remove the excess oil to prevent detrimental effects thereof. Referring to FIG. 5, in accordance with the principles of the present invention, a first passage  48  is provided in gland plate  32  that leads to a second passage  50  in housing  12 , which further leads to a receiver, and in the one embodiment, an internal cavity  53 . Accordingly, excess oil leaves space  40  through first passage  48 , within which it travels to second passage  50  in the crankcase housing. Oil then travels within second passage  50  to internal cavity  53 . In the preferred embodiment, the internal cavity is elongated and accepts an elongated cartridge or insert  54 , also shown in FIG. 6, having an elongated portion formed of an absorbent material for absorbing the oil within internal cavity  53 . Within the scope of the invention, the cavity could have other shapes or configurations, with a complimentary shaped cartridge or insert. In the preferred embodiment, the cartridge  54 , includes an elongated absorbent portion  56  and a connecting portion  58 . The crankcase housing at the external end of cavity  53 , in one embodiment, is threaded to engage a threaded interface  59  of connecting portion  58  of cartridge  54 , securing the insert within cavity  53  for the absorption of oil. Other connection interfaces could be used as well such as a snap fit, tapered force fit or rotatably locking fit as long as such connections make an appropriate seal and secure connection, and allow the cartridge or insert to be easily removed for servicing. Threaded end  58  includes a weep hole  60 . Hole  60  equalizes the pressure in the crankcase oil cavity with atmospheric pressure, allowing the oil to drain freely from the crankcase oil cavity to the internal oil cavity  53 . The weep hole  60  further acts as a visual indicator as to when the cartridge  54  is full of oil, and replacement is needed, as oil will begin to weep from the hole when saturation is reached. Upon saturation, the cartridge can be removed in the field and replaced with a new cartridge, easing serviceability of the compressor. An alternative design to the absorbent cartridge described above is a cartridge or insert configured as described but with an integral well, as opposed to an absorbent material,- for collecting the excess lubricant, which could be removed and emptied. 
     In another embodiment, an external collection reservoir, as shown in FIG. 7, is used as the receiver. Accordingly, reservoir  70  is mounted to the compressor housing  12  via a bolt  71  and includes an inlet  72  mounted to an outlet  74 , shown in FIG. 8, on housing  12 . Inlet  72  receives oil from outlet  74  which receives oil from passage  50 , which is diverted similar to as described above from space  40  (See FIG.  5 ), but for this embodiment, to the outlet  74 . Outlet  74  is preferably threaded  75  but inlet  72  of reservoir  70  is not so that an interface is formed between the inlet and outlet which allows the excess oil to pass to the reservoir while also allowing a pressure venting action to occur. The threads allow for a path through which the pressure can be vented. Accordingly, oil is collected in the external reservoir and can be emptied while being serviced. 
     Alternatively, as shown in FIG. 9, in place of the external reservoir, a tube  80  is used as the receiver and is attached via connecting end  81  to housing  12  at outlet  74 , through which oil can be directed for draining. As shown in FIG. 9, tube  80  includes a preformed segment  82 , connected to vertically, downward extending tube-portion  84 . Segment  82  is U-shaped, forming a trap which will fill with waste-compressor or excess oil being drained, and will prevent atmospheric moisture and debris from entering back into the compressor housing via the tube. While the invention has been described in reference to a preferred embodiment and a particular type of compressor, it is to be understood by those skilled in the art that modifications and variations can be effected within the spirit and scope of the invention and the invention could be applied to different types of compressors or other mechanisms incorporating similar type shaft seals.