Patent Document

BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an air compressor and, more particularly, to a pre-start lubrication system for an air compressor. 
         [0003]    2. Description of Related Art 
         [0004]    Often during startup of a compressor there is a period of time that the lubrication system of the compressor will not have full pressure. In particular, when the compressor is shut down, the oil pressure within the compressor quickly bleeds back to an oil sump. With the passageways of the lubrication system emptied of oil, when the compressor is restarted, it will run without lubrication or with partial lubrication for a period of time until the passages are once again filled and pressurized. This period of time will vary based on several factors. 
         [0005]    Many compressors were originally designed for continuous operation. However, since the addition of electric motor drive, start/stop operation has become the standard method of control. For compressor applications where hundreds of starts may be required each month, the accumulated result of periods during startup without full lubrication may result in reduced compressor life. 
         [0006]    While not generally known in the compressor field, it is known to provide pre-oiler systems in connection with internal combustion engines. However, U.S. Pat. No. 6,550,258 to Shoulders discloses pre-start bearing lubrication for a refrigeration system compressor. Many types of engine pre-oilers have been previously provided in an attempt to pre-oil certain moving parts of an engine prior to the engine being adequately oiled or lubricated by the engine lubrication system. One such system is disclosed in U.S. Pat. Nos. 5,348,121 and 5,244,059 to McLaughlin. This patent discloses the use of a normally closed, solenoid operated valve interposed in an oil line and which permits oil passage through the line to the engine when activated to the open position. Another example of pre-lubrication adapted to lubricate an engine at start-up is disclosed by U.S. Pat. No. 5,694,896 to Melvin. This patent discloses a simple pre-oiler that has a hollow pressure vessel and a control valve tapped into the engine oil system. The control valve has a plug which is balanced by the engine oil pressure and the vessel pressure. Finally, U.S. Pat. No. 3,556,070 to Holcomb discloses a solenoid valve pre-oiler lubricating device as another example of a pre-oiler system used in connection with an internal combustion engine. 
         [0007]    Another method of providing pre-lubrication in the field of internal combustion engines is to utilize a pre-start oil pump which augments the main lubrication pump for the engine. One such example is disclosed in U.S. Pat. No. 5,511,522 to Tran. U.S. Pat. No. 6,349,692 to Reinosa disclose the use of an electric pre-oiler pump for an internal combustion engine that is controlled by an external controller and is located within the engine. U.S. Pat. No. 4,893,598 to Stasuik discloses a manually-activated positive displacement pump as a pre-oiler device in an internal combustion engine. U.S. Pat. No. 4,834,039 to Apostolides discloses a multistage pre-lubricant pump. U.S. Pat. No. 4,703,727 to Cannon discloses a pre-start engine lubrication system for an internal combustion engine in which an external source of pressurized oil is connected through an engine oil filter port to lubricate the engine passageways before the engine starting mechanism is engaged. Additional pre-lubrication devices for internal combustion engines are disclosed in U.S. Pat. Nos. 5,236,064 to Wagoner; 5,156,120 to Kent; 3,583,525 to Holcomb; and 2,838,039 to Smith et al. Finally, U.S. Pat. No. 3,637,048 to Mount discloses an auxiliary oil pump for a centrifugal compressor which operates in the event of power failure to a main oil pump for the centrifugal compressor. 
         [0008]    In view of the foregoing, a need exists for a pre-start lubrication system that is desirably adapted of use with an air compressor. 
       SUMMARY OF THE INVENTION 
       [0009]    Generally, a pre-lubrication system is described herein and is provided to augment the normal lubrication system of an air compressor. The pre-lubrication system is generally intended to be operated just prior to operation of the air compressor to ensure that pressurized oil is available during start-up of the air compressor. In one embodiment, air compressor pre-lubrication system comprises an oil pump, a priming tank, and a control valve. The oil pump is connected to an oil sump and comprises a discharge line connected to an air compressor. The priming tank is connected to the oil pump to receive pressurized oil. The control valve is provided in an outline line connected to the priming tank and is further connected to the oil pump discharge line. The priming tank is configured to maintain a charge of oil from the oil pump and selectively release the charge of oil through actuation of the control valve. 
         [0010]    The control valve may comprise a solenoid valve. The priming tank may comprise a volume at least equal to the volumetric sum of lubrication passageways in the air compressor. The priming tank may comprise a diaphragm adapted to force oil into the discharge line upon actuation of the control valve. An inlet check valve may be disposed upstream of the priming tank. An outlet check valve may be disposed upstream of the control valve. The priming tank may be fluidly connected to the oil sump via sump return line and an oil pump relief valve. 
         [0011]    In another embodiment, the air compressor pre-lubrication system comprises an oil pump and an auxiliary pre-lubrication oil pump. The oil pump is connected to an oil sump and comprises a discharge line connected to an air compressor. The pre-lubrication oil pump is connected to the oil sump and is further fluidly coupled to the discharge line leading to the air compressor. The pre-lubrication pump may be adapted to provide pressurized oil to the discharge line prior to operation of the air compressor. The pre-lubrication pump may comprise an electric pump. 
         [0012]    Another aspect described herein relates to a method of pre-lubricating an air compressor comprising the steps of storing a charge of oil in a priming tank during normal operation of the air compressor, maintaining the charge of oil in the priming tank during stoppage of the air compressor, and selectively releasing the charge of oil before air compressor start-up to provide pressurized lubrication to the air compressor. 
         [0013]    The step of releasing the charge of oil may comprise actuation of a control valve. The control valve may comprise a solenoid valve. The priming tank may comprise a volume at least equal to the volumetric sum of lubrication passageways in the air compressor. The priming tank may comprise a diaphragm and the method may further comprise the diaphragm forcing oil into the discharge line upon actuation of a control valve. The step storing a charge of oil in the priming tank may be accomplished by an oil pump fluidly coupled to the priming tank. The method may further comprise preventing return flow to the oil pump with an inlet check valve provided upstream of the priming tank. The step of releasing the charge of oil may comprise actuation of a control valve and an outlet check valve is provided upstream of the control valve. 
         [0014]    Further details and advantages will be made clear upon consideration of the following description with reference to the accompanying drawings, all of which form a part of this specification, and wherein like reference numerals designate like part throughout. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic view of an air compressor pre-lubrication system according to one embodiment. 
           [0016]      FIG. 2  is a schematic view of an air compressor pre-lubrication system according to another embodiment. 
           [0017]      FIG. 3  is a schematic view of an air compressor pre-lubrication system according to a further embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    For purposes of the description hereinafter, spatial orientation terms, as used, shall relate to the referenced embodiment as it is oriented in the accompanying drawing figures or otherwise described in the following detailed description. However, it is to be understood that the embodiments described hereinafter may assume many alternative variations and configurations. It is also to be understood that the specific devices, features, and components illustrated in the accompanying drawing figures and described herein are simply exemplary and should not be considered as limiting. 
         [0019]    Referring to  FIG. 1 , an air compressor pre-lubrication system  20  is schematically shown. Pre-lubrication system  20  is provided to augment the normal lubrication system of an air compressor  45  and is intended to be operated just prior to operation of the air compressor  45  to ensure that pressurized oil is available during start-up of the air compressor  45 . Without pre-lubrication system  20 , during air compressor start-up, there would be a time when the air compressor  45  lacks full pressure lubrication. For applications where air compressor  45  must be started repeatedly, the accumulated result of these periods without full pressure lubrication will likely result in reduced life. 
         [0020]    In general, pre-lubrication system  20 , according to one exemplary embodiment, works by charging a priming tank (described herein) with pressurized oil during normal operation of air compressor  45 . When air compressor  45  is shut down, this priming tank maintains lubrication oil at normal system operating pressure for the air compressor  45 . When it is desired to start air compressor  45 , just prior to such start-up, the priming tank is “released” to be in fluid communication with the lubrication passages (not shown) of air compressor  45 . In this manner, full pressure lubrication is available at the moment of air compressor start-up. 
         [0021]    Pre-lubrication system  20  is adapted to work in conjunction with an air compressor oil lubrication pump  40 , as shown in  FIG. 1 . Oil pump  40  comprises an oil pump cavity  42  in fluid communication via an oil pump inlet valve  23  and inlet line  25  to an oil sump  27 . Oil pump cavity  42  of oil pump  40  is further in fluid communication with oil sump  27  via an outlet relief valve  30  and a sump return line  32 . Oil pump  40  provides lubrication oil to the lubrication passageways (not shown) of an air compressor  45  via an oil pump discharge valve  34  and discharge line  36 . 
         [0022]    Oil pump  40  is adapted to provide lubrication oil under pressure to pre-lubrication system  20  in accordance with the present embodiment. In the present embodiment, a branch line  50  is connected to the oil pump cavity  42  and includes a first or inlet check valve  52 . Branch line  50  connects to a priming tank  55  to provide pressurized lubrication oil to the priming tank  55 . Priming tank  55  is fluidly connected to discharge line  36  via an outlet line  56  comprising a control valve  57 , desirably a solenoid valve, and a second check valve  60 . As is apparent from  FIG. 1 , priming tank  55  is positioned between first check valve  52  and control valve  57  such that the first check valve  52  allows oil flow from oil pump cavity  42  to the priming tank  55  but prevents return flow from the priming tank  55  to the oil pump cavity  42 . Second check valve  60  is positioned downstream from control valve  57  and prevents return flow of oil from the second check valve  60  towards the control valve  57 . A choke  65  and oil pressure indicator  67  are also connected to discharge line  36  to monitor the system oil pressure for the air compressor  45 . 
         [0023]    Priming tank  55  is desirably a small reservoir with a diaphragm such as an expansion tank. Priming tank  55  is slightly larger in volume than the volumetric sum of the air compressor&#39;s lubrication passageways. During operation of oil pump  40 , priming tank  55  is charged with oil pressure generally equal to the operating pressure of air compressor  45  via branch line  50  which is connected to the oil pump cavity  42 . As is typical, when the air compressor  45  is shut down the oil pressure within the air compressor  45  quickly bleeds back to the oil sump  27 . In prior art arrangements, with the lubrication passageways emptied of oil, when the air compressor is restarted it will run without lubrication or with partial lubrication for a period of time until the passages are once again filled and pressurized lubrication oil. However, with pre-lubrication system  20  in place as shown in  FIG. 1 , priming tank  55  maintains a ready charge of oil pressure after shutdown. This pressurized oil is introduced back into the lubrication passageways in air compressor  45  via energizing control valve  57  (e.g., a solenoid valve) just prior to restarting air compressor  45 . The diaphragm in priming tank  55  acts to force oil into the lubrication passageways in air compressor  45  maintaining oil pressure until the air compressor  45  starts. When air compressor  45  is started, it is already at approximately normal operating pressure avoiding the period of partial lubrication. Priming tank  55  is then recharged by oil pump  40  so that the process may repeat. 
         [0024]    Referring to  FIG. 2 , another embodiment of the air compressor pre-lubrication system  20  is shown. In  FIG. 2 , like parts are identified with like reference numerals as found in  FIG. 1 . Pre-lubrication system  20  of  FIG. 2  is generally similar to that shown in  FIG. 1  except that priming tank  55  is located in-line before outlet relief valve  30  and sump return line  32 . Accordingly, pre-lubrication system  20  of  FIG. 2  is generally adapted to work in conjunction with air compressor oil lubrication pump  40  in generally the same manner as shown in  FIG. 1 . Referring now to  FIG. 2 , oil pump  40  comprises an oil pump cavity  42  in fluid communication via oil pump inlet valve  23  and inlet line  25  to oil sump  27 . As indicated, priming tank  55  is located in-line and upstream of outlet relief valve  30  and sump return line  32  leading to oil sump  27 . Oil pump  40  provides lubrication oil to the lubrication passageways (not shown) of air compressor  45  via oil pump discharge valve  34  and discharge line  36  in like manner to that shown in  FIG. 1 . 
         [0025]    Oil pump  40  is adapted to provide lubrication oil under pressure to pre-lubrication system  20  in accordance with the present embodiment. In the present embodiment, branch line  50  is connected to the oil pump cavity  42  and includes a first or inlet check valve  52 . Branch line  50  connects to priming tank  55  to provide pressurized lubrication oil to the priming tank  55 . Priming tank  55  is fluidly connected to discharge line  36  via outlet line  56  comprising control valve  57 , desirably a solenoid valve, and a second check valve  60 . As is apparent from  FIG. 2 , priming tank  55  is again positioned between first check valve  52  and control valve  57  such that the first check valve  52  allows oil flow from oil pump cavity  42  to the priming tank  55  but prevents return flow from the priming tank  55  to the oil pump cavity  42 . Second check valve  60  is positioned downstream from control valve  57  and prevents return flow of oil from the second check valve  60  towards the control valve  57 . A choke  65  and oil pressure indicator  67  is also connected to discharge line  36  to monitor the system oil pressure for the air compressor  45 . 
         [0026]    Priming tank  55  is desirably a small reservoir with a diaphragm such as an expansion tank. Priming tank  55  is slightly larger in volume than the volumetric sum of the air compressor&#39;s lubrication passageways. During operation of oil pump  40 , priming tank  55  is charged with oil pressure generally equal to the operating pressure of air compressor  45  via branch line  50  which is connected to the oil pump cavity  42 . As is typical, when the air compressor  45  is shut down, the oil pressure within the air compressor  45  quickly bleeds back to the oil sump  27 . In prior art arrangements, with the lubrication passageways emptied of oil, when the air compressor is restarted it will run without lubrication or with partial lubrication for a period of time until the passages are once again filled and pressurized with lubrication oil. However, with pre-lubrication system  20  in place as shown in  FIG. 2 , priming tank  55  maintains a ready charge of oil pressure after shutdown. This pressurized oil is introduced back into the lubrication passageways in air compressor  45  via energizing control valve  57  (e.g., a solenoid valve) just prior to restarting air compressor  45 . The diaphragm in priming tank  55  acts to force oil into the lubrication passageways in air compressor  45  maintaining oil pressure until the air compressor  45  starts. When air compressor  45  is started, it is already at approximately normal operating pressure avoiding the period of partial lubrication. Priming tank  55  is then recharged by oil pump  40  so that the process may repeat. 
         [0027]    Referring to  FIG. 3 , another embodiment of pre-lubrication system  20  is shown and wherein like parts are again identified with like reference numerals to those used in  FIG. 1 . In  FIG. 3 , oil pump  40  again comprises an oil pump cavity  42  in fluid communication via an oil pump inlet valve  23  and inlet line  25  to an oil sump  27 . Oil pump cavity  42  of oil pump  40  is further in fluid communication with oil sump  27  via an outlet relief valve  30  and a sump return line  32 . Oil pump  40  provides lubrication oil to the lubrication passageways (not shown) of an air compressor  45  via an oil pump discharge valve  34  and discharge line  36 . 
         [0028]    In  FIG. 3 , pre-lubrication system  20  comprises an auxiliary oil pump  70  connected to oil sump  27  via an inlet feed line  72 . A discharge line  74  from auxiliary oil pump  70  is connected to discharge line  36  leading to air compressor  45  and includes an auxiliary or second check valve  60  in like manner to previous embodiments. A choke  65  and oil pressure indicator  67  is also connected to discharge line  36  to monitor the system oil pressure for the air compressor  45 . The auxiliary oil pump  70  may be an electric pump located in the oil sump  27  of a crankcase associated with air compressor  45 . The auxiliary oil pump  70  is capable of providing oil to the air compressor  45  at pressure and flow rate generally equal to that of the main air compressor pump. During operation of the air compressor pre-lubrication system  20 , when air compressor  45  is shut down, the oil pressure within the air compressor  45  quickly bleeds back to oil sump  27 . Prior to re-starting the air compressor  45 , the auxiliary oil pump  70  is powered before the air compressor drive motor is started and provides lubrication to the air compressor  45  substantially at normal operating pressure thereby avoiding a period of partial lubrication. Once the air compressor drive motor has started and the main air compressor pump is operating at full capacity, the auxiliary oil pump  70  may be shutdown. Accordingly, by providing an auxiliary oil pump  70  to provide substantially normal oil pressure to air compressor  45  prior to start-up of the air compressor  45 , periods of partial or no lubrication are desirably eliminated and the operating life of the air compressor  45  is extended. 
         [0029]    While the foregoing discussion describes several embodiments of pre-lubrication system  20 , each of these embodiments may be provided as an external addition to the physical structure of air compressor  45  (e.g., an add-on type design) or, alternatively, as an internal adjunct to the air compressor  45 . Accordingly, the various embodiments of pre-lubrication system  20  described hereinabove may be provided external to or internal to the air compressor  45 . In the internal configuration, it may be desirable for control valve  57  to be external from the physical structure of air compressor  45 . 
         [0030]    While embodiments of an air compressor pre-lubrication system were provided in the foregoing description, those skilled in the art may make modifications and alterations to these embodiments without departing from the scope and spirit of the invention. Accordingly, the foregoing description is intended to be illustrative rather than restrictive. The invention described hereinabove is defined by the appended claims and all changes to the invention that fall within the meaning and the range of equivalency of the claims are to be embraced within their scope.

Technology Category: 2