Abstract:
A lubrication system that transfers sequential defined quantities of lubrication oil to lubrication points comprises: a lubrication oil reservoir for storing the lubrication oil; at least one positive displacement metering capsule; and a transfer valve for each capsule that alternately transfers lubrication oil from the lubrication oil reservoir to its respective capsule and from its respective capsule to its respective lubrication points; wherein each capsule increases its volume to receive the lubrication oil when its respective transfer valve transfers lubrication oil from the lubrication oil reservoir and decreases its volume to discharge lubrication oil when its respective transfer valve transfers lubrication oil to its respective lubrication points.

Description:
FIELD OF THE INVENTION  
       [0001]    The invention relates to lubrication systems, and more particularly to lubrication systems that dispense low quantities of lubrication oil. 
       BACKGROUND OF THE INVENTION  
       [0002]    Gas turbine engines for short-life expendable applications commonly employ rolling element bearings to journal rotating engine parts. Adequate lubrication of such bearings is essential to meeting designed life and reliability requirements. Long-life non-expendable engines use recirculating oil lubrication systems to secure optimal bearing life. However, such recirculating oil systems are not suitable for expendable engines due to their complexity, weight and cost. 
         [0003]    Expendable short-life engines also have design requirements that include maintenance-free long-term storage without servicing prior to use. One example of a lubrication system for expendable engines that does not incur the limitations of complexity, weight, cost, leakage and restricted storage conditions of recirculating oil lubrication systems is a so-called “constant loss” non-recirculating lubrication system. It comprises an oil reservoir and a simple delivery mechanism. The delivery mechanism supplies fresh oil to the bearings that flows through them and then through the engine flow path. There is no recirculation of the supplied oil so that lubrication only continues as long as the reservoir can deliver oil. The advantages of this system comprise its simplicity, size and weight. 
         [0004]    Such a constant loss lubrication system requires accurate metering of lubrication flow to the bearings under a wide variety of operating conditions in order to maximize operating time with a limited quantity of lubrication oil in the reservoir. Such operating conditions may comprise temperatures ranging from minus 40 to plus 80 degrees C. and altitudes ranging from sea level to 10 kilometres. It is generally difficult to accurately dispense small quantities of oil in a true volumetric positive displacement manner with such a variation of temperatures and altitudes due to corresponding changes in lubrication oil viscosity, oil supply pressure and variation in atmospheric backpressure whilst retaining a small, lightweight and low cost lubrication system. Attempts to do so using piston pumps with inlet and outlet valves, peristaltic pumps, metering solenoid valves and so forth have met with mixed results. 
       SUMMARY OF THE INVENTION  
       [0005]    The invention generally comprises a lubrication system for transferring sequential defined quantities of lubrication oil to lubrication points, comprising: a lubrication oil reservoir for storing the lubrication oil; at least one positive displacement metering capsule; and a transfer valve for each capsule that alternately transfers lubrication oil from the lubrication oil reservoir to its respective capsule and from its respective capsule to its respective lubrication points; wherein each capsule increases its volume to receive the lubrication oil when its respective transfer valve transfers lubrication oil from the lubrication oil reservoir and decreases its volume to discharge lubrication oil when its respective transfer valve transfers lubrication oil to the lubrication points. 
     
    
     
       DESCRIPTION OF THE DRAWINGS  
         [0006]      FIG. 1  is a schematic diagram of a lubrication system according to a first possible embodiment of the invention. 
           [0007]      FIG. 2  is a cut-away side view of a positive displacement metering capsule for the first possible embodiment of the invention. 
           [0008]      FIG. 3  is a schematic diagram of a lubrication system according to a second possible embodiment of the invention. 
           [0009]      FIG. 4  is a cut-away side view of a positive displacement metering capsule for the second possible embodiment of the invention. 
           [0010]      FIG. 5  is a lubrication system according to a third possible embodiment of the invention. 
           [0011]      FIG. 6  is a cut-away side view of a positive displacement metering capsule for the third possible embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]      FIG. 1  is a schematic diagram of a lubrication system  2  according to a first possible embodiment of the invention. The lubrication system  2  comprises a lubrication oil tank  4  for storing a quantity of lubrication oil. A lubrication oil transfer valve  6  couples the lubrication oil tank  4  to one side of a positive displacement metering capsule  8  when the lubrication oil transfer valve  6  is in a first state by way of a tank line  10  and a transfer valve line  12 . The lubrication oil transfer valve  6  couples the capsule  8  to lubrication points  14 , such as engine bearings, when the lubrication oil transfer valve  6  is in a second state by way of the transfer valve line  12  and a lubrication line  16 . 
         [0013]    The lubrication oil transfer valve  6  may be a three-way valve as shown in  FIG. 1 , with the lubrication oil tank  4  coupled to the actuator  8  when the lubrication oil transfer valve  6  is in a de-energized state and with the lubrication points  14  coupled to the capsule  8  when the lubrication oil transfer valve is in an energized state. The lubrication oil transfer valve  6  may comprise an electrically operated valve, such as a solenoid-operated valve as shown in  FIG. 1 , or a piezoelectric element-operated valve. It may also comprise a mechanically, pneumatically or hydraulically operated valve. 
         [0014]    The capsule  8  may comprise a hydraulic-pneumatic capsule or actuator, and it may be of the piston, bellows or diaphragm type. The displacement of the capsule  8  comprises a difference in volume between a maximum volume when it fills with lubrication oil and a minimum volume when it has discharged lubrication oil.  FIG. 2  is a cut-away side view of the hydraulic capsule  8  of with a movable partition of the diaphragm type. Referring to  FIGS. 1 and 2  together, a gas supply valve  18  couples to the other side of the capsule  8  by means of a gas valve line  20 . When the gas supply valve  18  is in a first state, it couples the capsule  8  to ambient atmosphere. When the gas supply valve  18  is in a second state, it couples the capsule  8  to an gas source  22 , typically by way of an gas source line  24 , a pressure regulating valve (PRV)  26  and a PRV line  28 , although if the gas source  22  has a sufficiently stable pressure, the gas source line  24  may couple directly to the gas supply valve  18 . The gas source  22  is typically an engine air compressor as shown in  FIG. 1 , although it may alternatively be another type of gas source, such as a compressed gas reservoir. In any case, the working gas may be air or any other convenient working gas and references to gas herein refers to air and any other working gas. 
         [0015]    The gas supply valve  18  may be a three-way valve as shown in  FIG. 1 , with the vessel  8  coupled to ambient atmosphere when the gas supply valve  18  is in a de-energized state and with the vessel  8  coupled to the gas source  20  when the gas supply valve  18  is in a de-energized state. The gas supply valve  18  may comprise a solenoid-operated valve as shown in  FIG. 1 , or it may comprise a mechanically, pneumatically or hydraulically operated valve. 
         [0016]    The vessel  8  has a moveable partition  30  mounted within a cavity  32 . The partition  30  may comprise an elastomeric suspension-supported diaphragm as shown in  FIG. 2  or a pre-tensioned metallic diaphragm. Alternatively, the partition  30  may comprise a piston or bellows. A portion of the cavity  32  between the partition  30  and the lubrication line  16  forms a lubrication oil chamber  34  that has a changeable volume. A bias spring  36  within the lubrication oil chamber  34  applies force against the partition  30  to push it toward a side of the cavity  32  with the gas valve line  20 . When the lubrication oil transfer valve  6  switches to its first or de-energized state, it allows lubrication oil to flow from the lubrication oil reservoir  4  into the capsule  8  by means of the transfer valve line  12 . As the gas supply valve  18  switches to its first or de-energized state, gas within the capsule cavity  32  adjacent the gas valve line  20  exhausts to atmosphere by means of the gas valve line  20 . The bias spring  36  is then able to force the partition  30  against the side of the cavity  32  with the gas valve line  20  and increase the volume of the lubrication oil chamber  34 . As the lubrication oil chamber  34  increases volume, it sucks in lubrication oil by means of the transfer valve line  12 . 
         [0017]    When the lubrication oil transfer valve  6  switches to its second or energized state, it allows lubrication oil in the lubrication oil chamber  34  of the capsule  8  to flow to the lubrication points  14  by way of the transfer valve line  12  and the lubrication line  16 . As the gas supply valve  18  switches to its second or energized state, it allows compressed gas from the gas source  22  to flow to the capsule  8  by way of the gas valve line  20  and the gas source line  24  to let the diaphragm  30  overcome the force of the bias spring  36  and move against the side of the cavity  32  with the transfer valve line  12 , thereby driving the lubrication oil in the lubrication oil chamber  34  to the lubrication points  14 . Since the change in volume of the lubrication oil chamber  34  is a fixed quantity, the lubrication system  2  can time-sequence the first and second states of the lubrication oil transfer valve  6  and the gas supply valve  18  to sequentially transfer discrete defined quantities of lubrication oil to the lubrication points  14  at timed intervals. 
         [0018]      FIG. 3  is a schematic diagram of a lubrication system  38  according to a second possible embodiment of the invention. It has an advantage over the hereinbefore-described lubrication system  2  that comprises fewer components and no need for the gas source  22 . The lubrication system  38  substitutes a positive displacement metering capsule  40  for the capsule  8 . The capsule  40  may comprise a hydraulic actuator, and it may be of the piston, bellows or diaphragm type.  FIG. 4  is a cut-away side view of the capsule  40  of the diaphragm type. Referring to  FIGS. 3 and 4  together, the capsule  40  has the partition  30  mounted within the cavity  32 , much the same as for the capsule  8 . The partition  30  may comprise an elastomeric suspension-supported diaphragm as shown in  FIG. 4  or a pre-tensioned metallic diaphragm. Alternatively, the partition  30  may comprise a piston or bellows. A portion of the cavity  32  between the partition  30  and the transfer valve line  12  forms the lubrication oil chamber  34  that has a changeable volume. 
         [0019]    A bias spring  42  applies force against the partition  30  to push it toward a side of the cavity  32  with the transfer valve line  12 . A ferrous rod or armature  44  attached to the opposite side of the partition  30  extends out of the cavity  32  into a solenoid  46 . Energizing the solenoid  46  may apply force to the armature  44  to overcome the bias force of the bias spring  42  to pull the armature  44  out of the cavity  32  from a first relaxed state to a second extended state. A vent  48  through the side of the cavity  32  with the armature  44  exhausts to ambient atmosphere. 
         [0020]    When the lubrication oil transfer valve  6  switches to its second or energized state, it allows lubrication oil to flow from the lubrication oil reservoir  4  to the capsule  40  by means of the transfer valve line  12 . When the armature  44  switches to its second or extended state, such as by energizing the solenoid  46 , it pulls the partition  30  with it, thereby increasing the volume of the lubrication oil chamber  34 . As the lubrication oil chamber  34  increases in volume, it sucks in lubrication oil by means of the transfer valve line  12 . When the lubrication oil transfer valve  6  switches to its first or de-energized state, it allows lubrication oil in the lubrication oil chamber  34  to flow to the lubrication points  14  by way of the transfer valve line  12  and the lubrication line  16 . As the armature  44  switches to its first or relaxed state, such as by de-energizing the solenoid  46 , it allows the bias spring  42  to force the partition  30  toward the side of the cavity  32  with the transfer valve line  12 , thereby decreasing its volume and driving the lubrication oil in the cavity lubrication oil chamber  34  to the lubrication points  14 . 
         [0021]      FIG. 5  is a schematic diagram of a lubrication system  50  according to a third possible embodiment of the invention. It has an advantage over the hereinbefore-described lubrication systems  2  and  38  that comprises less power consumption and positive lubrication oil feed. The lubrication system  50  substitutes a pressurized lubrication oil tank  52  for the lubrication oil tank  4 . The lubrication oil tank  52  may comprise a gas-pressurized bladder-type accumulator and may have a gas pre-charge or alternatively it may have pressure supplied by way of the gas source  22 , typically by way of an gas source line  24 , a pressure regulating valve (PRV)  26  if the gas source  22  is not sufficiently stable and a PRV line  28  as hereinbefore described in connection with  FIG. 1 . 
         [0022]    The lubrication system  50  also substitutes a positive displacement metering capsule  54  for the hereinbefore-described capsules  8  and  40 . The capsule  54  may comprise a hydraulic-pneumatic capsule or actuator, and it may be of the piston, bellows or diaphragm type.  FIG. 6  is a cut-away side view of the capsule  54  of the diaphragm type. Referring to  FIGS. 5 and 6  together, the capsule  54  has the partition  30  mounted within the cavity  32 , much the same as for the capsules  8  and  40 . The partition  30  may comprise an elastomeric suspension-supported diaphragm as shown in  FIG. 4  or a pre-tensioned metallic diaphragm. Alternatively, the partition  30  may comprise a piston or bellows. A portion of the cavity  32  between the partition  30  and the transfer valve line  16  forms the lubrication oil chamber  34  that has a changeable volume. 
         [0023]    A bias spring  56  applies force against the partition  30  to push it toward a side of the cavity  32  with the transfer valve line  12 . A vent  58  through the side of the cavity  32  with the bias spring  56  exhaust to ambient atmosphere. When the lubrication oil transfer valve  6  switches to its second or energized state, it allows lubrication oil to flow from the lubrication oil reservoir  52  to the capsule  54  by means of the transfer valve line  12 . The pressure of the lubrication oil flowing into the lubrication oil chamber  34  overcomes the force of the bias spring  56  to fill the lubrication oil chamber  34  with lubrication oil. 
         [0024]    When the lubrication oil transfer valve  6  switches to its first or de-energized state, it allows lubrication oil in the lubrication oil chamber  34  to flow to the lubrication points  14  by way of the transfer valve line  12  and the lubrication line  16 . The force of the bias spring  56  the partition  30  toward the side of the cavity  32  with the transfer valve line  12 , thereby decreasing its volume and driving the lubrication oil in the cavity lubrication oil chamber  34  to the lubrication points  14 . 
         [0025]    Although the lubrication systems  2 ,  38  and  50  as hereinbefore described utilize a single respective capsule  8 ,  40  and  50  to transfer lubrication oil to lubrication points  14 , alternatively the lubrication systems  2 ,  38  and  50  may have multiple capsules  8 ,  40  and  54 , each supplying lubrication oil to a different respective lubrication point  14 . 
         [0026]    The described embodiments of the invention are only some illustrative implementations of the invention wherein changes and substitutions of the various parts and arrangement thereof are within the scope of the invention as set forth in the attached claims.