Patent Application
20090071754
The invention relates to lubrication systems, and more particularly to lubrication systems that dispense low quantities of lubrication oil.
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.
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.
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.
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.
The lubrication oil transfer valve 6 may be a three-way valve as shown in
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.
The gas supply valve 18 may be a three-way valve as shown in
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
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.
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.
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.
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.
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.
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.
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.
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.
